heliogram vs message

heliogram and message both are nouns.

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

As nouns, message is a hypernym of heliogram; that is, message is a word with a broader meaning than heliogram:

heliogram: a message transmitted by means of the sun's rays
message: a communication (usually brief) that is written or spoken or signaled

heliogram (noun)	message (noun)
a message transmitted by means of the sun's rays	content communicating a message; what something is about
	a communication (usually brief) that is written or spoken or signaled