windward vs downwind

windward is a noun but downwind is not a noun.

Word	Noun	Adjective	Verb	Adverb
windward	Yes	Yes	No	Yes
downwind	No	Yes	No	Yes

As adverbs, windward and downwind are synonyms defined as:

windward (noun)	downwind (noun)
the side of something that is toward the wind
the direction from which the wind is coming

windward (adjective)	downwind (adjective)
on the side exposed to the wind	towards the side away from the wind

windward (adverb)	downwind (adverb)
toward the wind	with the wind; in the direction the wind is blowing
	toward the wind