photoengraving vs halftone engraving

photoengraving and halftone engraving both are nouns.

Word	Noun	Adjective	Verb	Adverb
photoengraving	Yes	No	No	No
halftone engraving	Yes	No	No	No

As nouns, photoengraving and halftone engraving are synonyms defined as:

photoengraving and halftone engraving: an engraving used to reproduce an illustration

Other synonyms of photoengraving include halftone.

photoengraving (noun)	halftone engraving (noun)
an engraving used to reproduce an illustration	an engraving used to reproduce an illustration