message vs radiogram

message and radiogram both are nouns.

Word	Noun	Adjective	Verb	Adverb
message	Yes	No	Yes	No
radiogram	Yes	No	No	No

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

message: a communication (usually brief) that is written or spoken or signaled
radiogram: a message transmitted by wireless telegraphy

message (noun)	radiogram (noun)
content communicating a message; what something is about	a photographic image produced on a radiosensitive surface by radiation other than visible light (especially by X-rays or gamma rays)
a communication (usually brief) that is written or spoken or signaled	a message transmitted by wireless telegraphy