graybeard vs old codger

graybeard and old codger both are nouns.

Word	Noun	Adjective	Verb	Adverb
graybeard	Yes	No	No	No
old codger	Yes	No	No	No

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

graybeard: a man who is very old
old codger: used affectionately to refer to an eccentric but amusing old man

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

graybeard (noun)	old codger (noun)
a man who is very old	used affectionately to refer to an eccentric but amusing old man