legend vs caption

legend and caption both are nouns.

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

As nouns, legend and caption are synonyms defined as:

legend (noun)	caption (noun)
brief description accompanying an illustration	brief description accompanying an illustration
a story about mythical or supernatural beings or events	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

legend (verb)	caption (verb)
	provide with a caption, as of a photograph or a drawing