Word of the day · 5 June 2026

pernicious

/pərˈnɪʃəs/

adjective

Highly harmful, especially in a gradual or subtle way.

In a sentence

A pernicious rumor spread faster than the correction.
Sleep loss has a pernicious effect on judgment.
They warned that the loophole could have pernicious results.

In an image

Pretty vine slowly choking a healthy tree — Illustrative: a lovely vine that quietly kills a tree shows harm that works in a gradual way.

Origin

From Latin perniciosus (destructive), from pernicies (ruin, destruction), related to nex (violent death).

History

Pernicious has long named harms that corrupt or destroy. Medicine kept phrases like pernicious anemia; civic writing uses it for rumors, habits and policies that erode trust. The word stresses seriousness and often stealth. A pernicious effect may not look dramatic on day one.

Nearby words

harmful · destructive · insidious

Damage that works quietly until the cost is clear.

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