bay window vs bow window

bay window and bow window both are nouns.

Word	Noun	Adjective	Verb	Adverb
bay window	Yes	No	No	No
bow window	Yes	No	No	No

As nouns, bay window and bow window are synonyms defined as:

bay window and bow window: a window that sticks out from the outside wall of a house

bay window (noun)	bow window (noun)
a window that sticks out from the outside wall of a house	a window that sticks out from the outside wall of a house
slang for a paunch