impair

verb

1. (transitive)To weaken; to affect negatively; to have a diminishing effect on.

   “In 2016, it was announced that Jones had been diagnosed with primary progressive aphasia, a form of dementia that impairs the ability to communicate.”

2. (archaic, intransitive)To grow worse; to deteriorate.

   “Flesh may empaire,[…]but reason can repaire.”

adj

1. (obsolete)Not fit or appropriate; unsuitable.

   “giues he not till iudgement guide his bounty, / Nor dignifies an impaire thought with breath:”

noun

1. (obsolete)The act of impairing or deteriorating.
2. (obsolete)The fact of being impaired or having grown worse.
3. (obsolete)An impairment or deterioration.

   “Suppoſe a mans credit ſhould ſuffer an impair with thoſe whoſe cenſure is not to be valued; yet think, which is worſe, ſhame or ſin? Wilt thou ſin againſt God to ſave thy credit?”