seamster vs garmentmaker

seamster and garmentmaker both are nouns.

Word	Noun	Adjective	Verb	Adverb
seamster	Yes	No	No	No
garmentmaker	Yes	No	No	No

As nouns, garmentmaker is a hypernym of seamster; that is, garmentmaker is a word with a broader meaning than seamster:

Other hypernyms of seamster include dressmaker, garment-worker, garment worker, adult male, man.

seamster (noun)	garmentmaker (noun)
a person whose occupation is making and altering garments	a person who makes garments