radiogram vs X-ray

radiogram and X-ray both are nouns.

Word	Noun	Adjective	Verb	Adverb
radiogram	Yes	No	No	No
X-ray	Yes	No	No	No

As nouns, X-ray is a hyponym of radiogram; that is, X-ray is a word with a more specific, narrower meaning than radiogram:

radiogram: a photographic image produced on a radiosensitive surface by radiation other than visible light (especially by X-rays or gamma rays)
X-ray: a radiogram made by exposing photographic film to X rays; used in medical diagnosis

Other hyponyms of radiogram include autoradiograph, roentgenogram, X-ray photograph, X-ray picture, X ray.

radiogram (noun)	X-ray (noun)
a photographic image produced on a radiosensitive surface by radiation other than visible light (especially by X-rays or gamma rays)	a radiogram made by exposing photographic film to X rays; used in medical diagnosis
a message transmitted by wireless telegraphy	electromagnetic radiation of short wavelength produced when high-speed electrons strike a solid target