louver vs spline

louver and spline both are nouns.

Word	Noun	Adjective	Verb	Adverb
louver	Yes	No	No	No
spline	Yes	No	No	No

As nouns, spline is a hypernym of louver; that is, spline is a word with a broader meaning than louver:

louver: one of a set of parallel slats in a door or window to admit air and reject rain
spline: a thin strip (wood or metal)

Other hypernyms of louver include slat.

louver (noun)	spline (noun)
one of a set of parallel slats in a door or window to admit air and reject rain	a thin strip (wood or metal)
	a flexible strip (wood or rubber) used in drawing curved lines