casement vs window sash

casement and window sash both are nouns.

Word	Noun	Adjective	Verb	Adverb
casement	Yes	No	No	No
window sash	Yes	No	No	No

As nouns, window sash is a hypernym of casement; that is, window sash is a word with a broader meaning than casement:

casement: a window sash that is hinged (usually on one side)
window sash: a framework that holds the panes of a window in the window frame

Other hypernyms of casement include sash.

casement (noun)	window sash (noun)
a window sash that is hinged (usually on one side)	a framework that holds the panes of a window in the window frame