improvement vs recovery

improvement and recovery both are nouns.

Word	Noun	Adjective	Verb	Adverb
improvement	Yes	No	No	No
recovery	Yes	No	No	No

As nouns, recovery is a hyponym of improvement; that is, recovery is a word with a more specific, narrower meaning than improvement:

improvement (noun)	recovery (noun)
the act of improving something	the act of regaining or saving something lost (or in danger of becoming lost)
a change for the better; progress in development	return to an original state
a condition superior to an earlier condition	gradual healing (through rest) after sickness or injury