signer vs endorser

signer and endorser both are nouns.

Word	Noun	Adjective	Verb	Adverb
signer	Yes	No	No	No
endorser	Yes	No	No	No

As nouns, endorser is a hyponym of signer; that is, endorser is a word with a more specific, narrower meaning than signer:

signer: someone who signs and is bound by a document
endorser: a person who transfers his ownership interest in something by signing a check or negotiable security

Other hyponyms of signer include cosignatory, cosigner, cosigner, abhorrer, indorser, attestant, attestator, attestor, witness.

signer (noun)	endorser (noun)
someone who signs and is bound by a document	someone who expresses strong approval
someone who can use sign language to communicate	a person who transfers his ownership interest in something by signing a check or negotiable security