morning vs greeting

morning and greeting both are nouns.

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

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

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

Other hypernyms of morning include farewell, word of farewell, salutation.

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