black tie vs bow-tie

black tie and bow-tie both are nouns.

Word	Noun	Adjective	Verb	Adverb
black tie	Yes	No	No	No
bow-tie	Yes	No	No	No

As nouns, bow-tie is a hypernym of black tie; that is, bow-tie is a word with a broader meaning than black tie:

Other hypernyms of black tie include bow tie, bowtie.

black tie (noun)	bow-tie (noun)
a black bow tie worn with a dinner jacket	a man's tie that ties in a bow
semiformal evening dress for men