Words / C2

del-uh-TEERR-ee-uh-s/ˌdeləˈtɪəriəs/

Deleterious means harmful, often gradually or in a way you might miss. Scientists and careful essayists prefer it to harmful when discussing effects on health, trust, or an ecosystem. In speech always say harmful; deleterious belongs on the page.

Meaning

Harmful, often in a gradual or hidden way.

Examples

• “Lack of sleep has a deleterious effect on memory.”
• “The policy had deleterious effects on small farms.”
• “Even mild dehydration can be deleterious to concentration.”

Good to know

Often of effects, slightly clinical. Everyday: harmful.

Near in meaning

harmful

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