English Reference
Verb

impair

v.
C1 Advanced US /ˌɪmˈpɛɹ/ UK /ɪmpˈeə/ im·pair UK spelling impairs

v.to make something less effective or worse. You use this when a person or thing is not working as well as it should.

v.to reduce the effectiveness, quality, or value of something; to cause a loss of physical or mental ability.


SIMPLE

The heavy rain began to impair the driver's vision.

CONTEXTUAL

The new law aims to prevent substances that might impair a pilot's judgment from being used before a flight.

COMPLEX

While the initial damage was minor, the constant exposure to saltwater eventually began to impair the structural integrity of the ancient stone walls.

Usage impair performance · significantly impair

Birth tourism also … impairs the executive branch’s ability to protect the national security.” Protection of national security was one of the grounds Roberts specifically cited in Trump v.

The Conversation· 19 Aug 2026

From Middle English impairen, empeiren, from Old French empeirier, from Early Medieval Latin impeiōrāre, from in- + Late Latin peiōrāre (“worsen”), from peiōrem (“worse”), comparative of malus (“bad”).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin la-lat peiōrō
Level C1 · Advanced
Frequency Occasional
Updated