ventilation vs improvement

ventilation and improvement both are nouns.

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

As nouns, improvement is a hypernym of ventilation; that is, improvement is a word with a broader meaning than ventilation:

ventilation (noun)	improvement (noun)
the act of supplying fresh air and getting rid of foul air	the act of improving something
the bodily process of inhalation and exhalation; the process of taking in oxygen from inhaled air and releasing carbon dioxide by exhalation	a change for the better; progress in development
a mechanical system in a building that provides fresh air	a condition superior to an earlier condition
free and open discussion of (or debate on) some question of public interest