unlawful carnal knowledge vs criminal congress

unlawful carnal knowledge and criminal congress both are nouns.

Word	Noun	Adjective	Verb	Adverb
unlawful carnal knowledge	Yes	No	No	No
criminal congress	Yes	No	No	No

As nouns, unlawful carnal knowledge and criminal congress are synonyms defined as:

unlawful carnal knowledge and criminal congress: forbidden or tabu sexual intercourse between individuals

unlawful carnal knowledge (noun)	criminal congress (noun)
forbidden or tabu sexual intercourse between individuals	forbidden or tabu sexual intercourse between individuals