welt vs seam

welt and seam both are nouns.

Word	Noun	Adjective	Verb	Adverb
welt	Yes	No	Yes	No
seam	Yes	No	Yes	No

As nouns, seam is a hypernym of welt; that is, seam is a word with a broader meaning than welt:

welt (noun)	seam (noun)
a raised or strengthened seam	joint consisting of a line formed by joining two pieces
a raised mark on the skin (as produced by the blow of a whip); characteristic of many allergic reactions	a stratum of ore or coal thick enough to be mined with profit
	a slight depression or fold in the smoothness of a surface

welt (verb)	seam (verb)
put a welt on	put together with a seam
beat severely with a whip or rod