dormer window vs dormer

dormer window and dormer both are nouns.

Word	Noun	Adjective	Verb	Adverb
dormer window	Yes	No	No	No
dormer	Yes	No	No	No

As nouns, dormer window and dormer are synonyms defined as:

dormer window and dormer: a gabled extension built out from a sloping roof to accommodate a vertical window

dormer window (noun)	dormer (noun)
a gabled extension built out from a sloping roof to accommodate a vertical window	a gabled extension built out from a sloping roof to accommodate a vertical window
the window in a gabled extension built to accommodate a window