Vane (noun)

A flat surface on a rotating object, such as a windmill or weather vane, that is used to indicate the direction of the wind or weather.

Origin:

Old english fana "flag, banner, standard", of germanic origin; related to dutch vaandel and german fahne.

Examples:

1. The wind vane on the roof showed that the wind was blowing from the north.
2. He mounted a weather vane on the roof to track the direction of the storms.
3. The vane on the wind turbine showed that it was not generating power.
4. The vane on the ship's mast was pointing east.
5. The vane on the spinning wheel indicated that the machine was in operation.