white tie vs tail coat

white tie and tail coat both are nouns.

Word	Noun	Adjective	Verb	Adverb
white tie	Yes	No	No	No
tail coat	Yes	No	No	No

As nouns, white tie and tail coat are synonyms defined as:

white tie and tail coat: formalwear consisting of full evening dress for men

Other synonyms of white tie include dress suit, full dress, tailcoat, tails, white tie and tails.

white tie (noun)	tail coat (noun)
bow tie worn as part of a man's formal evening dress	formalwear consisting of full evening dress for men
formalwear consisting of full evening dress for men