living room vs sitting room

living room and sitting room both are nouns.

Word	Noun	Adjective	Verb	Adverb
living room	Yes	No	No	No
sitting room	Yes	No	No	No

As nouns, living room and sitting room are synonyms defined as:

living room and sitting room: a room in a private house or establishment where people can sit and talk and relax

Other synonyms of living room include front room, living-room, parlor, parlour.

living room (noun)	sitting room (noun)
a room in a private house or establishment where people can sit and talk and relax	a room in a private house or establishment where people can sit and talk and relax