storm window vs storm sash

storm window and storm sash both are nouns.

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

As nouns, storm window and storm sash are synonyms defined as:

storm window and storm sash: a window outside an ordinary window to protect against severe weather or winter

storm window (noun)	storm sash (noun)
a window outside an ordinary window to protect against severe weather or winter	a window outside an ordinary window to protect against severe weather or winter