old man vs vernacular

old man and vernacular both are nouns.

Word	Noun	Adjective	Verb	Adverb
old man	Yes	No	No	No
vernacular	Yes	Yes	No	No

old man (noun)	vernacular (noun)
an informal term for your father	the everyday speech of the people (as distinguished from literary language)
a man who is very old	a characteristic language of a particular group (as among thieves)
a familiar term of address for a man
(slang) boss
aromatic herb of temperate Eurasia and North Africa having a bitter taste used in making the liqueur absinthe

old man (adjective)	vernacular (adjective)
	being or characteristic of or appropriate to everyday language