white tie vs dress suit

white tie and dress suit both are nouns.

Word	Noun	Adjective	Verb	Adverb
white tie	Yes	No	No	No
dress suit	Yes	No	No	No

As nouns, white tie and dress suit are synonyms defined as:

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

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

white tie (noun)	dress suit (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