A vane is a flat piece of material that moves or points in response to wind or water. The most familiar kind is a weather vane, which sits on top of barns, churches, and houses, spinning to show which direction the wind is blowing. These often have decorative shapes like roosters or arrows.

Windmills use vanes (also called blades) to catch the wind and convert its energy into mechanical power for grinding grain or pumping water. Modern wind turbines work the same way, using enormous blades to generate electricity.

You'll also find vanes inside machines: a fan has vanes that push air around, and airplane engines use vanes to direct airflow. Even arrows and darts have small vanes (called fletching on arrows) near the back to keep them flying straight.

Don't confuse vane with vain (overly proud) or vein (a blood vessel). All three words sound identical but mean completely different things.