liaison vs sexual relationship

liaison and sexual relationship both are nouns.

Word	Noun	Adjective	Verb	Adverb
liaison	Yes	No	No	No
sexual relationship	Yes	No	No	No

As nouns, sexual relationship is a hypernym of liaison; that is, sexual relationship is a word with a broader meaning than liaison:

liaison (noun)	sexual relationship (noun)
a channel for communication between groups	a relationship involving sexual intimacy
a usually secretive or illicit sexual relationship