viscera vs viscus

viscera and viscus both are nouns.

Word	Noun	Adjective	Verb	Adverb
viscera	Yes	No	No	No
viscus	Yes	No	No	No

As nouns, viscus is a hypernym of viscera; that is, viscus is a word with a broader meaning than viscera:

viscera: internal organs collectively (especially those in the abdominal cavity)
viscus: a main organ that is situated inside the body

Other hypernyms of viscera include internal organ.

viscera (noun)	viscus (noun)
internal organs collectively (especially those in the abdominal cavity)	a main organ that is situated inside the body