dress suit vs tails

dress suit and tails both are nouns.

Word	Noun	Adjective	Verb	Adverb
dress suit	Yes	No	No	No
tails	Yes	No	No	No

As nouns, dress suit and tails are synonyms defined as:

dress suit and tails: formalwear consisting of full evening dress for men

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

dress suit (noun)	tails (noun)
formalwear consisting of full evening dress for men	formalwear consisting of full evening dress for men