weathercock vs weathervane

weathercock and weathervane both are nouns.

Word	Noun	Adjective	Verb	Adverb
weathercock	Yes	No	No	No
weathervane	Yes	No	No	No

As nouns, weathervane is a hypernym of weathercock; that is, weathervane is a word with a broader meaning than weathercock:

weathercock: weathervane with a vane in the form of a rooster
weathervane: mechanical device attached to an elevated structure; rotates freely to show the direction of the wind

Other hypernyms of weathercock include vane, weather vane, wind vane.

weathercock (noun)	weathervane (noun)
weathervane with a vane in the form of a rooster	mechanical device attached to an elevated structure; rotates freely to show the direction of the wind