familiar vs old

familiar and old both are nouns.

Word	Noun	Adjective	Verb	Adverb
familiar	Yes	Yes	No	No
old	Yes	Yes	No	No

familiar (noun)	old (noun)
a spirit (usually in animal form) that acts as an assistant to a witch or wizard	past times
a person attached to the household of a high official (as a pope or bishop) who renders service in return for support
a friend who is frequently in the company of another

familiar (adjective)	old (adjective)
well known or easily recognized	of long duration; not new
within normal everyday experience; common and ordinary; not strange	(used especially of persons) having lived for a relatively long time or attained a specific age
having mutual interests or affections; of established friendship	skilled through long experience
(usually followed by `with') well informed about or knowing thoroughly	(used for emphasis) very familiar
	excellent
	just preceding something else in time or order
	belonging to some prior time