peristome vs complex body part

peristome and complex body part both are nouns.

Word	Noun	Adjective	Verb	Adverb
peristome	Yes	No	No	No
complex body part	Yes	No	No	No

As nouns, complex body part is a hypernym of peristome; that is, complex body part is a word with a broader meaning than peristome:

peristome: region around the mouth in various invertebrates
complex body part: a particular complex anatomical part of a living thing and its construction and arrangement

Other hypernyms of peristome include anatomical structure, bodily structure, body structure, structure.

peristome (noun)	complex body part (noun)
region around the mouth in various invertebrates	a particular complex anatomical part of a living thing and its construction and arrangement
(botany) fringe of toothlike appendages surrounding the mouth of a moss capsule