Impair/ɪmˈper/ Definition 1 of 3Pro Tip 1/3Slight Damage Impair indicates a partial, rather than a complete, decline in function or condition. Overworking might impair your health slightly, but not ruin it. Pro Tip 2/3Negative Outcome Using 'impair' suggests that the effect or outcome is negative or undesirable. Poor lighting can impair visibility on the road. Pro Tip 3/3Not Permanent The damage or weakening implied by 'impair' is often temporary or reversible. Lack of sleep may impair cognition until you can rest.