English words starting with I

572 words, from I to Itself. Levels A1 to C2. Each one opens a full lesson.

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Ipronoun · The speaker, used as the subject.A1 Icenoun · Frozen water, hard and cold.A1 Ice Creamnoun · A sweet frozen food made from milk or cream.A1 Ice Lollynoun · A piece of flavoured ice on a stick (British).A1 Icebergnoun · A very large piece of ice floating in the sea.A1 Icingnoun · A sweet covering on a cake, often white or coloured (British).A1 Icing Sugarnoun · Very fine sugar used for icing and dusting cakes (UK; US powdered sugar).B1 Iconnoun · A small picture on a screen; also a famous person or symbol that represents something.B2 Iconoclastnoun · A person who attacks popular beliefs or established ways of doing things.C2 Ideanoun · A thought or plan in your mind.A1 Idealadjective · Perfect, or the best that can be imagined in the circumstances.B2 Ideallyadverb · In a perfect situation; if things were as you would like.B2 Identicaladjective · Exactly the same in every way.B1 Identifiableadjective · Able to be recognised or named.C1 Identificationnoun · An official document that proves who you are; also the act of recognising someone or something.B1 Identifyverb · To recognise someone or something and say who or what they are.B1 Identitynoun · Who a person is, or the qualities that make a person or group different.B1 Ideologicaladjective · Relating to a system of political or social beliefs.C1 Ideologuenoun · A person who follows a political or social belief system very strictly.C1 Ideologynoun · A set of beliefs that guide a person or group.C1 Idiomnoun · A phrase whose meaning is not obvious from the separate words.B2 Idiomaticadjective · Using language in a natural, native-like way; of an expression, not literal.C1 Idiosyncrasynoun · A distinctive, often peculiar, habit or feature of one person or thing.C2 Idiosyncraticadjective · Peculiar to one person; unusual in a personal way.C2 Idleadjective · Not working or being used; also lazy (often critical).B2 Ifconjunction · Used to talk about a possible situation.A1 Igloonoun · A round house made of snow, used in very cold places.A1 Igniteverb · To start burning, or to cause strong feeling or conflict to start.C1 Ignominiousadjective · Shameful and embarrassing, especially after a public failure (formal).C2 Ignorancenoun · Lack of knowledge or information (not a synonym of stupidity).C1 Ignorantadjective · Not knowing about something; also rude through lack of awareness.B2 Ignoreverb · To pay no attention to someone or something.A2 Illadjective · Not well; sick.A1 Ill-Advisedadjective · Unwise; showing poor judgement.C1 Illegaladjective · Not allowed by the law.B1 Illegallyadverb · In a way that breaks the law.B1 Illegitimateadjective · Not allowed by law or rules; formerly, born to unmarried parents.C1 Illicitadjective · Not allowed by law or by the rules.C1 Illiterateadjective · Unable to read or write; also ignorant in a particular field (computer-illiterate).C1 Illnessnoun · A period of being unwell, or a particular type of disease.B1 Illuminateverb · To light something up; also to make an idea clearer.B2 Illusionnoun · A false idea or appearance; something that seems true but is not.C1 Illusoryadjective · Not real, though it seems so; based on a false idea.C1 Illustrateverb · To explain something by giving examples or pictures.B2 Illustrationnoun · A picture in a book; also an example that makes an idea clearer.B1 Illustriousadjective · Famous and highly respected for achievement (formal).C2 Imagenoun · A picture, or the way that people think of a person or organisation.B1 Imagerynoun · Descriptive language that creates pictures in the mind (usually uncountable).B2 Imaginaryadjective · Existing only in the mind; not real.B1 Imaginationnoun · The ability to form new ideas or pictures in the mind (often uncountable).B1 Imaginativeadjective · Good at thinking of new and interesting ideas.B1 Imagineverb · To form a picture or idea in your mind.B1 Imbalancenoun · A lack of equal amounts or fair proportions.B2 Imbroglionoun · A complicated, confusing, and embarrassing situation.C2 Imbueverb · To fill someone or something with a feeling, quality, or idea (imbue with).C2 Imitateverb · To copy the way someone speaks, looks, or behaves.B2 Imitationnoun · A copy of something, often cheaper or less authentic; also the act of copying.B2 Immaculateadjective · Perfectly clean, or without any fault.C2 Immaterialadjective · Not important in this situation; also not consisting of physical matter.C1 Immatureadjective · Not fully developed; of behaviour, childish for the person’s age.C1 Immeasurableadjective · Too large, great, or extreme to be measured.C1 Immediateadjective · Happening now, without delay; also nearest (the immediate area).B1 Immediatelyadverb · At once; without any delay.A2 Immenseadjective · Extremely large or great.B2 Immerseverb · To involve yourself deeply in an activity, or to put something completely in liquid.C1 Immersionnoun · The state of being deeply involved, or of being put completely into a liquid.C1 Immigrantnoun · A person who comes to live permanently in a new country.B1 Immigrationnoun · The process of coming to live in a country that is not your own (usually uncountable).B1 Imminentadjective · Almost certain to happen very soon.C1 Immobiliseverb · To prevent someone or something from moving or working (UK spelling).C1 Immoraladjective · Not considered morally acceptable.C1 Immortaladjective · Living or lasting forever; of fame, never forgotten.C1 Immuneadjective · Protected against a disease; also not affected by something (immune to).B1 Immuniseverb · To protect someone against a disease by vaccination (UK spelling).B2 Immunitynoun · Protection from a disease, or from a legal penalty.B2 Immutableadjective · Unable to be changed (formal).C2 Impactnoun · A strong effect on someone or something.B1 Impairverb · To weaken or damage the quality or function of something.C1 Impairmentnoun · A weakening or damage of a function; also a loss of value.C1 Impartverb · To pass on information, knowledge, or a quality (formal).C1 Impartialadjective · Fair because you do not support one side.B1 Impartialitynoun · Fairness that comes from not supporting one side.C1 Impassenoun · A situation in which no further progress is possible.C1 Impassionedadjective · Showing strong feeling, especially in speech or writing.C1 Impatientadjective · Annoyed because you have to wait, or eager for something to happen now.B1 Impeachverb · To charge a public official with a serious offence; also to challenge the honesty of a witness.C1 Impeachmentnoun · The process of charging a public official with a serious offence.C1 Impeccableadjective · Without any faults or mistakes; perfect in behaviour or taste.C2 Impecuniousadjective · Having little or no money (formal).C2 Impedeverb · To delay or block the progress of something.C1 Impedimentnoun · Something that delays or blocks progress.C1 Impelverb · To force or strongly urge someone to do something (formal).C1 Impendingadjective · About to happen, usually something unpleasant (formal).C1 Impenetrableadjective · Impossible to get through, or impossible to understand.C1 Imperativeadjective · Extremely important and needing immediate action; also a grammar mood, or (noun) a vital duty.C1 Imperceptibleadjective · Too slight, gradual, or faint to be noticed.C1 Imperialadjective · Relating to an empire; also the UK non-metric system of units.B2 Imperialismnoun · A policy of extending a country’s power over other lands, especially by force or economic control.C1 Imperialistnoun · A person or policy that seeks to extend empire or domination over others.C1 Imperilverb · To put someone or something in danger (formal).C1 Imperiousadjective · Expecting to be obeyed; arrogantly commanding.C2 Impersonaladjective · Not showing personal feeling; also not linked to a particular person.C1 Imperturbableadjective · Remaining calm and not easily upset or excited.C2 Imperviousadjective · Not affected or influenced; also not allowing liquid to pass through.C1 Impetuousadjective · Acting quickly, without thought; rash (formal).C2 Impetusnoun · Something that encourages a process or activity to happen more quickly.C1 Impingeverb · To have an effect, usually unwelcome (impinge on / upon).C1 Implacableadjective · Unable to be calmed, satisfied, or persuaded to change (formal).C2 Implantverb · To put something into the body in a medical procedure; also to fix an idea in someone’s mind.C1 Implausibleadjective · Not seeming reasonable or likely to be true.C1 Implementverb · To start using a plan or system.B2 Implementationnoun · The process of putting a plan, law, or policy into action.B2 Implicateverb · To show that someone is involved in a crime or fault (implicate in); also to suggest as a consequence.C1 Implicationnoun · A possible result, or something suggested without being said directly.C1 Implicitadjective · Suggested but not stated directly.C1 Implodeverb · To collapse inwards; of an organisation, to fail suddenly from within.C1 Implyverb · To suggest something without saying it directly.B2 Importnoun · A product brought in from another country; also the act of bringing it in.B1 Importancenoun · The quality of being important (uncountable; of importance).B1 Importantadjective · Something you must care about or take seriously.A1 Importuneverb · To ask someone persistently and pressingly for something (formal).C2 Imposeverb · To force a rule, tax, or burden on someone; also to take unfair advantage (impose on).C1 Imposingadjective · Large and impressive in appearance.C1 Impositionnoun · An unwelcome demand or burden; also the act of imposing a rule or tax.C1 Impossibleadjective · Not able to be done or to happen.A2 Impoverishedadjective · Made poor; also made weaker in quality.C1 Imprecationnoun · A spoken curse (formal / literary).C2 Impreciseadjective · Not exact or accurately expressed.C1 Impregnableadjective · Impossible to capture, break into, or overcome.C2 Impressverb · To make someone admire you or feel respect.B1 Impressionnoun · The opinion or feeling you have about someone or something.B1 Impressiveadjective · Making you admire something because it is very good or large.B1 Imprintnoun · A mark left by pressure; also a lasting effect, or a publisher’s brand name.C1 Imprisonverb · To put someone in prison.B2 Imprisonmentnoun · The state of being in prison; a prison sentence.B2 Improbableadjective · Not likely to be true or to happen.C1 Impromptuadjective · Done without being planned or prepared.C1 Improperadjective · Not suitable, honest, or in accordance with rules.C1 Improprietynoun · Behaviour that is dishonest, or not suitable for the situation (formal).C1 Improveverb · To become better, or to make something better.A2 Improvementnoun · A change that makes something better, or the process of becoming better.B1 Improviseverb · To invent or provide something without preparation, using what you have.B2 Imprudentadjective · Not showing care for the consequences; unwise (formal).C1 Impudentadjective · Rude and disrespectful in a cheeky, shameless way.C2 Impugnverb · To call someone’s honesty, motives, or accuracy into question (formal).C2 Impulsenoun · A sudden desire to act, without much thought; also a short electrical or physical push.C1 Impulsiveadjective · Acting suddenly without thinking carefully.B2 Impunitynoun · Freedom from punishment or the usual harmful results (with impunity).C2 Imputeverb · To say that someone or something is the cause or source of a fault (impute to) (formal).C1 Inpreposition · Inside a place, or during a month, year, or part of the day.A1 Inabilitynoun · The fact of not being able to do something (usually uncountable).B2 Inaccessibleadjective · Impossible or very hard to reach, obtain, or understand.C1 Inaccurateadjective · Not correct or not exact.B1 Inactionnoun · Failure to do anything, especially when action is needed.C1 Inadequacynoun · The state of not being enough, or not being good enough.C1 Inadequateadjective · Not enough, or not good enough.B1 Inadvertentadjective · Not intentional; done by accident.C1 Inalienableadjective · Unable to be taken away or given up (formal, of a right).C1 Inaneadjective · Silly, empty, and without meaning (disapproving).C2 Inappropriateadjective · Not suitable for the situation or for the people involved.B1 Inauguraladjective · Marking the beginning of an important job, event, or institution.C1 Inaugurateverb · To mark the official beginning of a post, building, or era.C1 Incalculableadjective · Too great to be measured or guessed; also impossible to calculate.C1 Incapableadjective · Not able to do something (incapable of).C1 Incapacitateverb · To make someone unable to work or act normally.C1 Incarcerateverb · To put someone in prison (formal).C1 Incendiaryadjective · Designed to cause fire; of remarks, likely to provoke anger.C2 Incentivenoun · Something that encourages you to do something.B2 Inceptionnoun · The beginning of an organisation, project, or process (formal).C1 Incessantadjective · Continuing without stopping, often in an annoying way.C1 Inchnoun · A unit of length; there are twelve inches in a foot.A2 Inchoateadjective · Just beginning and not yet fully formed (formal).C2 Incidencenoun · How often something, especially something bad, happens in a group or period.C1 Incidentnoun · Something that happens, especially something unusual or unpleasant.B1 Incidentaladjective · Happening as a minor accompaniment, not as the main point.C1 Incidentallyadverb · Used to add a less important fact; by the way.B2 Incipientadjective · Just beginning to appear or develop (formal).C1 Incisiveadjective · Clear, sharp, and cutting quickly to the point.C2 Inciteverb · To encourage people to act, especially in a violent or unlawful way.C1 Inclinationnoun · A feeling that you want to do something; a tendency.C1 Inclineverb · To lean or slope; to tend to think or behave in a particular way (incline to / towards).C1 Includeverb · To have something as a part of a group or whole.A2 Includingpreposition · Used to show that someone or something is part of a larger group.A2 Inclusionnoun · The practice of including people who might otherwise be left out (often uncountable).B1 Inclusiveadjective · Including everyone or everything mentioned; of a price, with all charges in.C1 Incoherentadjective · Not clear, logical, or well organised; hard to follow.C1 Incomenoun · The money that a person or organisation receives, usually from work.B1 Incomingadjective · Arriving, or about to start a job or term of office.B2 Incompatibleadjective · Unable to exist or work together without conflict.C1 Incompetencenoun · Lack of the skill or ability needed to do a job properly.C1 Incompetentadjective · Not having the skill or ability needed to do a job properly.C1 Incompleteadjective · Not finished, or missing necessary parts.B1 Incomprehensibleadjective · Impossible or extremely difficult to understand.C1 Inconceivableadjective · Impossible to imagine or believe.C1 Inconclusiveadjective · Not leading to a clear decision or result.C1 Incongruitynoun · The state of being strange because things do not match.C1 Incongruousadjective · Strange because it does not fit the surroundings or the rest.C2 Inconsequentialadjective · Not important; of no real consequence.C1 Inconsistencynoun · The fact of not matching or not staying the same; a specific mismatch.C1 Inconsistentadjective · Not staying the same; containing parts that contradict each other.B2 Inconspicuousadjective · Not easily seen or noticed.C1 Incontestableadjective · Impossible to question or deny.C1 Incontrovertibleadjective · Impossible to deny because the evidence is so strong.C2 Inconveniencenoun · Trouble or difficulty caused to someone; as a verb, to cause that trouble.B1 Incorporateverb · To include something as part of a whole.C1 Incorrectadjective · Wrong; not accurate or true.C1 Incorrectlyadverb · In a wrong way; not correctly.B2 Increaseverb · To become larger in number or amount, or to make something larger.A2 Increasingadjective · Becoming larger in amount or degree.B2 Increasinglyadverb · More and more.B1 Incredibleadjective · Extremely good or large; also hard to believe.B2 Incredulitynoun · The state of being unwilling or unable to believe something.C1 Incredulousadjective · Unable or unwilling to believe something.C2 Incrementnoun · A regular, often small, increase in amount or value.C1 Incrementaladjective · Happening in a series of small, regular additions.C1 Incriminateverb · To make someone appear guilty of a crime or fault.C1 Inculcateverb · To fix an idea or habit in someone’s mind by repeating it (formal).C1 Incumbentnoun · The person who currently holds a particular official position; also (adjective) incumbent on — required of.C1 Incurverb · To become subject to something unpleasant, especially a cost or a penalty, as a result of your actions.C1 Incursionnoun · A sudden entry into a place, especially a hostile or unwelcome one (formal).C1 Indebtedadjective · Owing money, or owing thanks (indebted to).C1 Indecentadjective · Offensive in a sexual way; also (indecent haste) unreasonably quick and improper.C1 Indecisiveadjective · Not able to make decisions quickly; of a result, not settling the question.C1 Indeedadverb · Used to emphasise that something is true, or to agree strongly.A2 Indefatigableadjective · Never giving up; seeming never to tire (formal).C2 Indefensibleadjective · Impossible to justify or to protect.C1 Indefiniteadjective · Not clear or fixed, or with no set end date.B2 Indelibleadjective · Impossible to remove or forget.C1 Indemnifyverb · To promise to pay someone if they suffer loss, or to pay that compensation.C1 Indemnitynoun · Protection against legal or financial loss; also a payment to cover loss.C1 Independencenoun · The state of being free from control by others (usually uncountable).B1 Independentadjective · Not needing help from other people, or not controlled by them.B1 Independentlyadverb · Without help or control from others; independently of means not depending on.B1 Indeterminateadjective · Not exactly known, fixed, or decided.C1 Indexnoun · A list at the back of a book; also a number that tracks prices or performance (a cost-of-living index).B1 Indicateverb · To show that something is true or likely.B1 Indicationnoun · A sign that something is true or likely (an indication of / that).B1 Indicativeadjective · Showing that something is likely or true (indicative of); also a grammar mood.C1 Indicatornoun · A fact or sign used to measure change; also a car’s flashing turn light (UK).B1 Indictverb · To formally accuse someone of a serious crime (said /ɪnˈdaɪt/).C1 Indictmentnoun · A formal accusation of a serious crime; also a sign that a system is badly at fault (an indictment of).C1 Indifferencenoun · Lack of interest or care; also, of quality, neither good nor bad.C1 Indigenousadjective · Originally from a place; native.C1 Indignantadjective · Angry because something is unfair or insulting.C2 Indignationnoun · Anger at something considered unfair or wrong.C1 Indignitynoun · Treatment that makes someone feel ashamed or unimportant.C1 Indirectadjective · Not done or said in a straight or obvious way; not going the shortest route.C1 Indiscriminateadjective · Done without careful choice or without thinking who is affected.C1 Indispensableadjective · So necessary that you cannot do without it.C1 Indisputableadjective · Impossible to deny because clearly true.C1 Indistinguishableadjective · Impossible to tell apart from something else (indistinguishable from).C1 Individualnoun · A single person, considered separately; as an adjective, for one person.B1 Individualismnoun · The belief that individual freedom matters more than collective control.C1 Indoctrinateverb · To teach a set of beliefs uncritically, especially political or religious ones.C1 Indolentadjective · Lazy; not wanting to work or be active (formal / literary).C2 Indomitableadjective · Impossible to defeat or discourage (formal / literary).C2 Indooradjective · Happening or used inside a building.B2 Indoorsadverb · Inside a building, not outside.A1 Induceverb · To persuade or cause something to happen; in medicine, to start a process deliberately.C1 Inducementnoun · Something offered to persuade someone to do something.C1 Inductionnoun · A formal introduction to a job or organisation; also reasoning from cases, or the act of inducing.C1 Indulgeverb · To allow yourself or someone else to have something enjoyable (indulge in / indulge someone).C1 Industrialadjective · Connected with factories and making goods.B1 Industrialiseverb · To develop industry on a large scale in a country or region (UK spelling).B2 Industriousadjective · Hard-working and diligent.C1 Industrynoun · The production of goods, or a type of business.B1 Ineffableadjective · Too great or extreme to be described in words.C2 Ineffectiveadjective · Not producing the result you want.B2 Ineffectualadjective · Not producing the intended result; weak and unsuccessful.C1 Inefficientadjective · Wasting time, money, or energy; not working well.B1 Ineligibleadjective · Not allowed to take part or to receive something under the rules.C1 Ineluctableadjective · Impossible to avoid; inescapable.C2 Ineptadjective · Clumsy, unskilful, or badly judged.C1 Inequalitynoun · An unfair difference in wealth, health, or opportunity (countable or uncountable).B1 Inequitynoun · A lack of fairness; an unfair situation (formal).C1 Inertadjective · Not moving, acting, or reacting; in chemistry, not readily combining.C1 Inertianoun · Unwillingness to change or act; in physics, resistance to a change in motion.C1 Inescapableadjective · Impossible to avoid or deny.C1 Inevitableadjective · Certain to happen and impossible to avoid.B2 Inevitablyadverb · In a way that cannot be avoided or prevented.B1 Inexorableadjective · Impossible to stop or persuade.C2 Inexpensiveadjective · Low in price; a more neutral word than cheap.B2 Inexperiencedadjective · Having little practice or knowledge of a job or activity.B2 Inexplicableadjective · Impossible to explain.C1 Inextricableadjective · Impossible to separate or to escape from.C1 Infallibilitynoun · The quality of never being wrong or never failing.C1 Infallibleadjective · Never wrong, or never failing.C1 Infamousadjective · Well known for something bad.C1 Infamynoun · The state of being well known for something bad (usually uncountable).C1 Infantnoun · A very young child; in England, infant school is for the youngest primary years.B1 Infectverb · To pass a disease to a person, animal, or plant.B1 Infectionnoun · An illness caused by bacteria or a virus.B1 Infectiousadjective · Able to spread from one person to another; also, of a mood, spreading easily.B1 Inferverb · To decide that something is true from the information you have, not from a direct statement.B2 Inferencenoun · A conclusion drawn from evidence rather than from a direct statement.B2 Inferioradjective · Lower in quality, rank, or status (inferior to).C1 Infiltrateverb · To enter a place or group secretly in order to spy on it or undermine it.C1 Infiltrationnoun · The act of entering a place or group secretly; also the slow entry of a liquid.C1 Infiniteadjective · Without any limit or end.B2 Inflameverb · To make a feeling, especially anger, more intense; also to make a body part red and swollen.C1 Inflammatoryadjective · Likely to stir anger or violence; also relating to swelling in the body.C1 Inflateverb · To fill with air; also to make a number or price rise in a misleading way.B1 Inflationnoun · A general rise in prices, so that money buys less.B1 Inflationaryadjective · Causing a general rise in prices, or relating to that rise.C1 Inflexibleadjective · Unwilling or unable to change; also stiff and hard to bend.C1 Inflictverb · To make someone suffer something unpleasant (inflict something on someone).B2 Influencenoun · The power to change how someone thinks or acts.B1 Influentialadjective · Having a lot of influence on people or events.C1 Influxnoun · The arrival of a large number of people or things.B2 Informverb · To tell someone facts (inform someone of / about / that).B1 Informaladjective · Relaxed and not official in style or dress.B1 Informantnoun · Someone who gives information, especially to the police or to a researcher.B2 Informationnoun · Facts or details about something.A2 Informativeadjective · Giving useful information.B1 Informedadjective · Having enough knowledge to decide well (an informed choice / informed consent).B1 Infrastructurenoun · The basic systems a society needs, such as roads, power, and internet.C1 Infringeverb · To break a law or right, or to limit someone’s freedom (infringe on / upon).C1 Infringementnoun · An act of breaking a law, right, or agreement.C1 Infuriateverb · To make someone extremely angry.C1 Infuseverb · To fill something with a quality or feeling; also to soak in liquid to extract flavour.C1 Ingeniousadjective · Clever at inventing things or solving problems in an original way.C1 Ingenuitynoun · Cleverness at inventing things or solving problems in an original way.C1 Ingenuousadjective · Innocent, frank, and often too trusting (formal; not ingenious).C2 Ingrainedadjective · Firmly fixed and difficult to change, of a habit, attitude, or dirt.C1 Ingratiateverb · To win favour by trying to please, often insincerely (ingratiate yourself with).C2 Ingredientnoun · One of the foods in a recipe; also one part of a plan or mix.B1 Inhabitverb · To live in a place.B2 Inhabitantnoun · A person or animal that lives in a particular place.B1 Inhaleverb · To breathe in air, gas, or smoke.C1 Inherentadjective · Existing as a natural part of something.C1 Inheritverb · To receive money, property, or a situation from someone after they die, or from the past.B1 Inheritancenoun · Money or property received from someone who has died; also a genetic trait.B2 Inhibitverb · To make an action or process more difficult or less likely; to hold someone back.C1 Inhumanadjective · Extremely cruel, or lacking human warmth; also not human.C1 Inimicaladjective · Harmful or unfriendly toward something.C2 Iniquitynoun · Gross wickedness, or a grossly unjust act (formal / literary).C2 Initialadjective · Happening at the beginning.B1 Initiallyadverb · At the beginning.B1 Initiateverb · To start a process or scheme, often an official one.C1 Initiativenoun · A new plan, or the ability to start things without being told.B1 Injectverb · To put a liquid into the body with a needle; also to put money or energy into a system.B1 Injectionnoun · The act of putting a drug into the body with a needle; also money put into a business or system.B1 Injunctionnoun · An official court order requiring someone to do, or not do, something.C1 Injureverb · To hurt a person or animal physically.B1 Injurynoun · Harm to a person’s body.B1 Injusticenoun · Unfair treatment, or an unfair event or situation.B2 Inknoun · A coloured liquid used in pens and printers for writing or printing.A1 Innateadjective · Existing from birth; natural rather than learned.C1 Inneradjective · On the inside; also private (inner thoughts); inner-city means central urban.B1 Innocentadjective · Not having done anything illegal or wrong.B1 Innocuousadjective · Not harmful or likely to offend.C2 Innovateverb · To introduce new methods, ideas, or products.C1 Innovationnoun · A new idea, method, or product.B2 Innovativeadjective · Introducing or using new ideas or methods.C1 Innuendonoun · An indirect remark that suggests something unpleasant, often sexual or damaging.C2 Innumerableadjective · Too many to be counted.C1 Inopportuneadjective · Happening at a bad or unsuitable time (formal).C1 Inordinateadjective · Far more than is reasonable or expected (formal).C2 Inputnoun · Information, ideas, or work put into a system or discussion; also a computing term.B2 Inquestnoun · An official inquiry, especially by a coroner into a sudden death (UK).B2 Inquireverb · To ask for information, especially formally (UK also enquire; inquire often for official investigation).C1 Inquirynoun · An official process to find out the facts; also a question (enquiry is common for everyday questions).B1 Inquisitiveadjective · Eager to know things; sometimes too curious.C1 Insaneadjective · Seriously mentally ill (dated or clinical care needed); informal: extremely unreasonable.C1 Inscribeverb · To write or cut words on a surface; also to dedicate a book to someone.C1 Inscriptionnoun · Words written or cut on a surface; also a dedication written in a book.C1 Inscrutableadjective · Impossible to understand or interpret.C2 Insectnoun · A small animal with six legs, such as a fly, ant, or bee.A1 Insecureadjective · Not confident; also not safe or not firmly fixed.B2 Insecuritynoun · Lack of confidence; also lack of safety, especially of a job or home.B2 Insensitiveadjective · Not noticing or caring about other people’s feelings; also not affected by something.C1 Insertverb · To put something into something else.B2 Insidepreposition · In the inner part of something.A1 Insidernoun · A person who belongs to an organisation and knows its private information.B2 Insidiousadjective · Spreading gradually in a harmful way that is hard to notice.C1 Insightnoun · A clear understanding of a complicated situation or idea.B2 Insignificantadjective · Too small or unimportant to be worth considering.B2 Insinuateverb · To suggest something unpleasant in an indirect way; also to work your way in.C2 Insipidadjective · Lacking flavour, interest, or liveliness.C2 Insistverb · To say firmly that something is true or must happen.B1 Insolentadjective · Rude and disrespectful, especially towards someone in authority.C2 Insolubleadjective · Impossible to solve; of a substance, that will not dissolve.C1 Insolvencynoun · The state of being unable to pay debts.C1 Insolventadjective · Unable to pay debts; bankrupt in effect.C1 Insomnianoun · The condition of finding it hard to sleep.B1 Insouciantadjective · Calm and not worried, sometimes in a way that seems careless.C2 Inspectverb · To look at something carefully in order to check it.B1 Inspectionnoun · An official visit to check that rules are being followed.B1 Inspectornoun · An official who checks that rules are followed; also a police rank.B1 Inspirationnoun · A person or thing that gives you new ideas; also a feeling of creative energy.B2 Inspireverb · To make someone feel they want to do something, or to give them a new idea.B1 Instabilitynoun · The state of being likely to change or collapse in an unwelcome way.C1 Installverb · To put a piece of equipment or software in place so it is ready to use.B1 Installationnoun · The act of putting equipment in place; also an artwork arranged in a space.B2 Instalmentnoun · One of several payments for something; also one part of a story published or broadcast over time.B1 Instancenoun · An example of something (for instance; in this instance).B1 Instantadjective · Happening immediately; also (of food) made very quickly (instant coffee).B1 Instantaneousadjective · Happening immediately, with no delay.C1 Instantlyadverb · Immediately; at once.B2 Insteadadverb · In the place of something else.A2 Instigateverb · To cause a process or event to start, especially something unwelcome.C1 Instigatornoun · A person who starts a process or event, especially something unwelcome.C1 Instilverb · To gradually put an idea, feeling, or habit into someone’s mind (UK spelling).C1 Instinctnoun · A natural tendency to behave in a particular way without thinking.B2 Instinctiveadjective · Done automatically, without conscious thought.B2 Institutenoun · An organisation that does research or education in a particular subject.B1 Institutionnoun · A large organisation such as a university, bank, or hospital.B1 Institutionaladjective · Relating to a large organisation such as a university, hospital, or government body.C1 Institutionaliseverb · To make something an accepted, permanent part of an organisation (UK spelling).C1 Instructverb · To tell someone officially to do something; also to teach a practical skill.B1 Instructionnoun · Information that tells you how to do something.B1 Instructornoun · A person who teaches a practical skill, such as driving or sport.B1 Instrumentnoun · A tool or device for a particular job, especially a musical one.B1 Instrumentaladjective · Playing an important part in making something happen (instrumental in); also of music without words.C1 Insubordinationnoun · Refusal to obey orders from someone in authority.C1 Insufficientadjective · Not enough (insufficient + noun; insufficient to + verb).B1 Insularadjective · Narrow in outlook, unwilling to meet other ideas; also of an island.C2 Insulateverb · To protect from heat, cold, or noise; also to protect from unwelcome influence.C1 Insultverb · To say or do something rude that offends someone.B1 Insurancenoun · An agreement in which you pay money so that you receive money if something bad happens.B1 Insureverb · To buy insurance so that you receive money if something is lost, damaged, or stolen.B1 Insurgentnoun · A person who fights against the government or occupying force.C1 Insurrectionnoun · A violent attempt to take control from the people in power.C1 Intactadjective · Complete and undamaged.B2 Intakenoun · The amount of food, drink, or air you take in; also the group of people accepted onto a course.B1 Intangibleadjective · Not able to be touched; of a quality, real but not physical.C1 Integraladjective · Being an essential part of something (integral to).B1 Integrateverb · To combine things so that they work as one, or to join a group.B2 Integrationnoun · The process of combining people or systems so they work as one (often uncountable).B1 Integritynoun · The quality of being honest and having strong moral principles.C1 Intellectnoun · The ability to think and understand, especially at a high level.C1 Intellectualadjective · Connected with serious thought and study; as a noun, a person who lives by ideas.B1 Intelligencenoun · The ability to learn, understand, and think.B1 Intelligentadjective · Able to learn, understand, and think well.A2 Intelligibleadjective · Able to be understood.C1 Intendverb · To have a plan or purpose.B1 Intendedadjective · Planned or meant (the intended meaning / audience).B1 Intenseadjective · Very strong, serious, or extreme.B1 Intensifyverb · To become or make something stronger or more extreme.B2 Intensitynoun · The strength of a feeling, light, effort, or activity.B2 Intensiveadjective · Involving a lot of effort, care, or attention in a short time.B1 Intentnoun · What someone means to do; their purpose (often with intent).B2 Intentionnoun · A plan or purpose; what you mean to do.B1 Interactverb · To communicate or work with someone or something (interact with).B1 Interactionnoun · The process of talking or working with other people or things.B1 Interactiveadjective · Allowing two-way communication or user control; involving people together.B2 Interceptverb · To stop something or someone before they reach a place.B2 Interdependencenoun · The state of depending on one another.C1 Interdisciplinaryadjective · Involving two or more academic subjects.C1 Interestnoun · A feeling of wanting to know more; also extra money from a bank.A2 Interestedadjective · Wanting to know or learn about something.A1 Interestingadjective · Holding your attention because it is unusual or useful.A2 Interfacenoun · A point where two systems meet; also the layout through which a user controls software.C1 Interfereverb · To get involved in a situation where you are not wanted, or to prevent something from working well (interfere with).B1 Interferencenoun · Unwanted involvement in something; also noise that spoils a signal.B2 Interimadjective · Temporary, until a final arrangement; also (noun) the intervening period (in the interim).C1 Interiornoun · The inside of a building or vehicle; also a government department in some countries.B1 Intermediarynoun · A person or body that passes messages or arranges a deal between two sides.C1 Intermediateadjective · Between two levels, places, or stages; neither basic nor advanced.B2 Intermittentadjective · Stopping and starting at intervals; not continuous.C1 Internnoun · A student or recent graduate who works for a short time to gain experience.B1 Internaladjective · Inside a person, organisation, or country rather than outside.B1 Internationaladjective · Involving two or more countries.B1 Internecineadjective · Destructive to both sides, especially of conflict within a group.C2 Internetnoun · The worldwide computer network for information and messages.A1 Internmentnoun · The act of holding people in prison or a camp, especially in wartime, without trial.C1 Internshipnoun · A short period of work with an organisation, usually to gain experience.B1 Interpretverb · To explain the meaning of something, or to understand it in a particular way.B2 Interpretationnoun · An explanation of the meaning of something; also spoken translation.B1 Interrogateverb · To ask someone many questions, especially officially or aggressively; also to query a system.C1 Interruptverb · To stop someone speaking or something happening for a short time.B1 Interruptionnoun · Something that stops a process or activity for a time.B2 Intersectverb · To cross or cut across; of groups or ideas, to overlap.C1 Intersectionnoun · A place or point where things cross; also overlap between groups or ideas.C1 Intersticenoun · A small intervening space; a gap (formal).C2 Intervalnoun · A period of time between two events; also a short break in a play or concert.B1 Interveneverb · To become involved in a situation in order to change it.B2 Interventionnoun · Action taken to change a situation, often to stop it getting worse.B1 Interviewnoun · A formal meeting to ask someone questions, often for a job.B1 Intimateadjective · Private and personal; also having a very close knowledge (intimate with / knowledge of); verb /ˈɪntɪmeɪt/ to hint.C1 Intimidateverb · To frighten someone in order to make them do what you want.B2 Intimidationnoun · The act of frightening someone in order to make them do, or not do, something.C1 Intopreposition · To the inside of a place or thing.A1 Intolerableadjective · Too bad, painful, or unfair to be accepted.C1 Intolerancenoun · Unwillingness to accept people or views you disagree with; also inability to take a food or drug.C1 Intolerantadjective · Not willing to accept behaviour, beliefs, or people you disagree with; also unable to take a food or drug.C1 Intonationnoun · The rise and fall of the voice in speaking.C1 Intractableadjective · Very hard to deal with, control, or solve.C2 Intransigencenoun · Refusal to change your views or to agree (formal).C1 Intransigentadjective · Refusing to change your views or agree to a compromise (formal).C2 Intrepidadjective · Very brave; not afraid of danger or difficulty (sometimes slightly ironic).C2 Intricateadjective · Having many small parts or details put together in a complicated way.C1 Intriguenoun · Secret plotting; also (verb /ɪnˈtriːɡ/) to interest someone a great deal.C1 Intrinsicadjective · Belonging to the true nature of something.C1 Introduceverb · To tell two people each other’s names, or to bring something new.B1 Introductionnoun · The opening of a book or talk; also the act of bringing something in for the first time.B1 Introductoryadjective · Serving as an introduction; intended for beginners.C1 Introspectionnoun · The examination of your own thoughts and feelings.C1 Introspectiveadjective · Tending to examine your own thoughts and feelings.C1 Intrudeverb · To enter a place or situation where you are not wanted (intrude on / upon).C1 Intuitionnoun · The ability to know something without conscious reasoning.C1 Inundateverb · To flood a place with water, or to overwhelm someone with things to deal with.C1 Inureverb · To become used to something unpleasant so that it no longer affects you (be inured to).C2 Invadeverb · To enter a country or space by force; also to enter in a way that is not wanted (invade privacy).B1 Invalidateverb · To make something legally or logically no longer valid.C1 Invaluableadjective · Extremely useful; so useful you cannot put a price on it (not “worthless”).B2 Invasionnoun · An armed attack that enters a country; also an unwelcome intrusion.B2 Invectivenoun · Angry, insulting language used to attack someone (formal).C2 Inveighverb · To speak or write with bitter hostility against someone or something (formal; inveigh against).C2 Inveigleverb · To persuade someone by deception or flattery (formal).C2 Inventverb · To make or design something that did not exist before.B1 Inventionnoun · Something new that someone has made or designed, or the act of making it.B1 Inventorynoun · A complete list of items; also the stock a business holds.B2 Inverseadjective · Opposite in nature, direction, or effect (the inverse of).C1 Invertverb · To turn something upside down, or to reverse its order or meaning.C1 Investverb · To put money, time, or effort into something in order to get a result later.B1 Investigateverb · To try to find out the facts about something.B1 Investigationnoun · A careful official examination of the facts of a situation or crime.B1 Investigatornoun · A person whose job is to examine a crime, accident, complaint, or research question.B2 Investmentnoun · Money, time, or effort put into something in order to get a result later.B1 Investornoun · A person or organisation that puts money into something in order to make a profit.B2 Inveterateadjective · Having a habit that has lasted a long time and is unlikely to change.C2 Invidiousadjective · Unpleasant and likely to cause resentment, especially of a comparison or choice (formal).C2 Invigilateverb · To watch candidates during an examination (UK).C1 Invisibleadjective · Impossible to see; also ignored or not counted.B2 Invitationnoun · A request asking someone to come to an event.A2 Inviteverb · To ask someone to come to an event or a place.A2 Invoicenoun · A document that lists goods or work and asks for payment.B1 Invokeverb · To use a law, right, or reason in support of something; also to call on a higher power, or cause a program to run.C1 Involuntaryadjective · Done without conscious control or without a real choice.C1 Involveverb · To include someone or something as a necessary part.B1 Involvedadjective · Taking part in something, or connected with it.A2 Involvementnoun · The fact of taking part in something, or of being connected with it.B1 Inwardadjective · Towards the inside; of thoughts, private rather than shown.C1 Irascibleadjective · Easily made angry (formal).C2 Iridescentadjective · Showing luminous colours that change with the angle of view.C2 Ironnoun · A strong metal used to make tools, machines, and some buildings.B1 Ironicadjective · Using words that mean the opposite of what you say; also oddly contrary to what you expect.B2 Ironicallyadverb · In an ironic way; used when the opposite of what you expect happens.B2 Ironingnoun · The job of making clothes smooth with an iron (often uncountable).B1 Ironing Boardnoun · A folding board with a padded top, used when you iron clothes.B1 Ironmongernoun · A shop, or shopkeeper, that sells tools, screws, and household hardware (UK).B1 Ironynoun · A contrast between expectation and reality, or saying the opposite of what you mean.B2 Irrationaladjective · Not based on reason or clear thinking.B2 Irrefutableadjective · Impossible to deny or disprove.C1 Irregularadjective · Not regular in shape, time, or rules.B2 Irregularitynoun · Something that is not according to the rules; also unevenness.C1 Irrelevantadjective · Not related to the subject and therefore not useful.B2 Irreparableadjective · Too badly damaged to be repaired.C1 Irreplaceableadjective · Too valuable, rare, or unique to be replaced if lost.C1 Irresistibleadjective · Too attractive or strong to refuse or fight.B2 Irrespectiveadjective · Without considering something; regardless (irrespective of).B2 Irresponsibleadjective · Not showing a sense of duty or care for the effects of your actions.B2 Irreverentadjective · Showing a lack of respect for people or things that are usually taken seriously.C2 Irreversibleadjective · Impossible to change back to a previous state.C1 Irrevocableadjective · Impossible to change, reverse, or take back (formal).C2 Irrigateverb · To supply land with water so that crops can grow.C1 Irritateverb · To annoy someone; also to make skin or eyes sore.B2 Irritationnoun · The feeling of being annoyed; also slight redness or inflammation.C1 Isverb · The form of “be” used with he, she, it, or a singular noun.A1 Islandnoun · A piece of land with water all around it.A1 Isolateverb · To keep someone or something separate from others.B1 Isolationnoun · The state of being separate from others; also a period of staying apart because of illness.B1 Isolationismnoun · A policy of staying out of the political or economic affairs of other countries.C1 Issuenoun · A problem or important topic.B1 Itpronoun · A thing, animal, or idea already mentioned; also the weather or time.A1 Itemnoun · A single thing in a list or a group.B1 Itemiseverb · To list each item separately (UK spelling).C1 Itinerantadjective · Travelling from place to place, especially to work (formal).C2 Itinerarynoun · A planned route or timetable for a journey.B2 Itsdeterminer · Belonging to a thing or animal: The cat ate its food. Not the same as it’s.A1 Itselfpronoun · It, used for emphasis or when a thing does something to itself.A1