weathervane vs weather vane

weathervane and weather vane both are nouns.

Word	Noun	Adjective	Verb	Adverb
weathervane	Yes	No	No	No
weather vane	Yes	No	No	No

As nouns, weathervane and weather vane are synonyms defined as:

weathervane and weather vane: mechanical device attached to an elevated structure; rotates freely to show the direction of the wind

Other synonyms of weathervane include vane, wind vane.

weathervane (noun)	weather vane (noun)
mechanical device attached to an elevated structure; rotates freely to show the direction of the wind	mechanical device attached to an elevated structure; rotates freely to show the direction of the wind