finish vs photo finish

finish and photo finish both are nouns.

Word	Noun	Adjective	Verb	Adverb
finish	Yes	No	Yes	No
photo finish	Yes	No	No	No

As nouns, photo finish is a hyponym of finish; that is, photo finish is a word with a more specific, narrower meaning than finish:

finish: designated event that concludes a contest (especially a race)
photo finish: in general, any very close finish; in particular, a finish of a race in which the contestants are so close together that the winner must be determined from a photograph taken at the instant of finishing

Other hyponyms of finish include draw, standoff, tie, runner-up finish, second-place finish, third-place finish.

finish (noun)	photo finish (noun)
the act of finishing	in general, any very close finish; in particular, a finish of a race in which the contestants are so close together that the winner must be determined from a photograph taken at the instant of finishing
a decorative texture or appearance of a surface (or the substance that gives it that appearance)
(wine tasting) the taste of a wine on the back of the tongue (as it is swallowed)
designated event that concludes a contest (especially a race)
the downfall of someone (as of persons on one side of a conflict)
event whose occurrence ends something
the place designated as the end (as of a race or journey)
a highly developed state of perfection; having a flawless or impeccable quality
the temporal end; the concluding time

finish (verb)	photo finish (verb)
finally be or do something
come or bring to a finish or an end
cause to finish a relationship with somebody
finish eating all the food on one's plate or on the table
provide with a finish
have an end, in a temporal, spatial, or quantitative sense; either spatial or metaphorical