adultery vs fornication

adultery and fornication both are nouns.

Word	Noun	Adjective	Verb	Adverb
adultery	Yes	No	No	No
fornication	Yes	No	No	No

As nouns, adultery and fornication are synonyms defined as:

adultery and fornication: extramarital sex that willfully and maliciously interferes with marriage relations

Other synonyms of adultery include criminal conversation.

adultery (noun)	fornication (noun)
extramarital sex that willfully and maliciously interferes with marriage relations	voluntary sexual intercourse between persons not married to each other
	extramarital sex that willfully and maliciously interferes with marriage relations