old man vs antique

old man and antique both are nouns.

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

As nouns, antique is a hyponym of old man; that is, antique is a word with a more specific, narrower meaning than old man:

Other hyponyms of old man include codger, old codger, gaffer, old-timer, old geezer, oldtimer, patriarch.

old man (noun)	antique (noun)
an informal term for your father	any piece of furniture or decorative object or the like produced in a former period and valuable because of its beauty or rarity
a man who is very old	an elderly man
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)	antique (adjective)
	made in or typical of earlier times and valued for its age
	out of fashion
	belonging to or lasting from times long ago

old man (verb)	antique (verb)
	give an antique appearance to
	shop for antiques