greeting vs morning

greeting and morning both are nouns.

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

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

greeting: (usually plural) an acknowledgment or expression of good will (especially on meeting)
morning: a conventional expression of greeting or farewell, used to wish someone a good morning

greeting (noun)	morning (noun)
(usually plural) an acknowledgment or expression of good will (especially on meeting)	a conventional expression of greeting or farewell, used to wish someone a good morning
	the earliest period
	the time period between dawn and noon
	the first light of day