endowment vs knack

endowment and knack both are nouns.

Word	Noun	Adjective	Verb	Adverb
endowment	Yes	No	No	No
knack	Yes	No	No	No

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

Other hyponyms of endowment include bent, hang, flair, genius, raw talent.

endowment (noun)	knack (noun)
the act of endowing with a permanent source of income	a special way of doing something
natural abilities or qualities
the capital that provides income for an institution