vernacular vs drop-dead

vernacular is a noun but drop-dead is not a noun.

Word	Noun	Adjective	Verb	Adverb
vernacular	Yes	Yes	No	No
drop-dead	No	No	No	Yes

vernacular (noun)	drop-dead (noun)
the everyday speech of the people (as distinguished from literary language)
a characteristic language of a particular group (as among thieves)

vernacular (adjective)	drop-dead (adjective)
being or characteristic of or appropriate to everyday language

vernacular (adverb)	drop-dead (adverb)
	stunningly or breathtakingly