full dress vs tails

full dress and tails both are nouns.

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

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

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

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

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