caption vs furnish

caption is a noun but furnish is not a noun.

Word	Noun	Adjective	Verb	Adverb
caption	Yes	No	Yes	No
furnish	No	No	Yes	No

As verbs, furnish is a hypernym of caption; that is, furnish is a word with a broader meaning than caption:

Other hypernyms of caption include offer, provide, render, supply.

caption (noun)	furnish (noun)
brief description accompanying an illustration
translation of foreign dialogue of a movie or TV program; usually displayed at the bottom of the screen
taking exception; especially a quibble based on a captious argument

caption (verb)	furnish (verb)
provide with a caption, as of a photograph or a drawing	give something useful or necessary to
	provide or equip with furniture