Vane

The weather vane points north.

That guy is a real weather vane: he constantly changes his mind.

Many a layman confuse vane with vain.

Vane and vain are homophones.

What a cute wind vane!

The wind blew the weather vane off the roof.

Mounted on the wind vane support is an anemometer, an instrument for measuring the velocity of the wind.

In nineteen eighty-two, British scientist Sir John Vane shared the Nobel Prize in Medicine in part for discovering how aspirin works. He found that aspirin blocks the body from making natural substances called prostaglandins.