chelicera vs appendage

chelicera and appendage both are nouns.

Word	Noun	Adjective	Verb	Adverb
chelicera	Yes	No	No	No
appendage	Yes	No	No	No

As nouns, appendage is a hypernym of chelicera; that is, appendage is a word with a broader meaning than chelicera:

chelicera: either of the first pair of fang-like appendages near the mouth of an arachnid; often modified for grasping and piercing
appendage: an external body part that projects from the body

Other hypernyms of chelicera include extremity, member.

chelicera (noun)	appendage (noun)
either of the first pair of fang-like appendages near the mouth of an arachnid; often modified for grasping and piercing	a part that is joined to something larger
	an external body part that projects from the body
	a natural prolongation or projection from a part of an organism either animal or plant