monochrome vs photo

monochrome and photo both are nouns.

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

As nouns, photo is a hypernym of monochrome; that is, photo is a word with a broader meaning than monochrome:

monochrome: a black-and-white photograph or slide
photo: a representation of a person or scene in the form of a print or transparent slide or in digital format

Other hypernyms of monochrome include exposure, photograph, pic, picture.

monochrome (noun)	photo (noun)
a black-and-white photograph or slide	a representation of a person or scene in the form of a print or transparent slide or in digital format
painting done in a range of tones of a single color

monochrome (adjective)	photo (adjective)
having or appearing to have only one color