greeting vs acknowledgement

greeting and acknowledgement both are nouns.

Word	Noun	Adjective	Verb	Adverb
greeting	Yes	No	No	No
acknowledgement	Yes	No	No	No

As nouns, acknowledgement is a hypernym of greeting; that is, acknowledgement is a word with a broader meaning than greeting:

greeting: (usually plural) an acknowledgment or expression of good will (especially on meeting)
acknowledgement: a statement acknowledging something or someone

Other hypernyms of greeting include acknowledgment.

greeting (noun)	acknowledgement (noun)
(usually plural) an acknowledgment or expression of good will (especially on meeting)	a statement acknowledging something or someone
	the state or quality of being recognized or acknowledged