peritoneum vs serous membrane

peritoneum and serous membrane both are nouns.

Word	Noun	Adjective	Verb	Adverb
peritoneum	Yes	No	No	No
serous membrane	Yes	No	No	No

As nouns, serous membrane is a hypernym of peritoneum; that is, serous membrane is a word with a broader meaning than peritoneum:

peritoneum: a transparent membrane that lines the abdominal cavity in mammals and covers most of the viscera
serous membrane: a thin membrane lining the closed cavities of the body; has two layers with a space between that is filled with serous fluid

Other hypernyms of peritoneum include serosa.

peritoneum (noun)	serous membrane (noun)
a transparent membrane that lines the abdominal cavity in mammals and covers most of the viscera	a thin membrane lining the closed cavities of the body; has two layers with a space between that is filled with serous fluid