heliogravure vs photogravure

heliogravure and photogravure both are nouns.

Word	Noun	Adjective	Verb	Adverb
heliogravure	Yes	No	No	No
photogravure	Yes	No	No	No

As nouns, heliogravure and photogravure are synonyms defined as:

Other synonyms of heliogravure include gravure.

heliogravure (noun)	photogravure (noun)
an intaglio print produced by gravure	using photography to produce a plate for printing
	an intaglio print produced by gravure
	printing from an intaglio plate prepared by photographic methods