photogravure vs heliogravure

photogravure and heliogravure both are nouns.

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

As nouns, photogravure and heliogravure are synonyms defined as:

Other synonyms of photogravure include gravure.

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