skiagraph vs photo

skiagraph and photo both are nouns.

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

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

skiagraph: a photographic image produced on a radiosensitive surface by radiation other than visible light (especially by X-rays or gamma rays)
photo: a representation of a person or scene in the form of a print or transparent slide or in digital format

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

skiagraph (noun)	photo (noun)
a photographic image produced on a radiosensitive surface by radiation other than visible light (especially by X-rays or gamma rays)	a representation of a person or scene in the form of a print or transparent slide or in digital format