last word vs smartness

last word and smartness both are nouns.

Word	Noun	Adjective	Verb	Adverb
last word	Yes	No	No	No
smartness	Yes	No	No	No

As nouns, last word and smartness are synonyms defined as:

Other synonyms of last word include chic, chichi, chicness, modishness, stylishness, swank.

last word (noun)	smartness (noun)
elegance by virtue of being fashionable	elegance by virtue of being fashionable
the final statement in a verbal argument	liveliness and eagerness
an authoritative statement	intelligence as manifested in being quick and witty
	a kind of pain such as that caused by a wound or a burn or a sore