Impair (verb)

1. To make worse or less effective; to damage or degrade.
2. To make weaker or less able.

Origin:

The word impair comes from the old french word empeirier, which means "to make worse" or "to damage".

Examples:

1. The accident impaired his ability to walk.
2. The disease impaired her vision.
3. The storm impaired the power lines and caused a blackout.
4. The delay impaired the schedule of the project.
5. The scandal impaired the reputation of the company.