Sheave (mechanical)

grooved wheel used for holding a belt, wire or rope; may have multiple grooves on a single wheel rotating parallelly; may be incorporated into a pulley; does not include an axle or a surrounding frame

A sheave (pronounced "sheev") is a wheel or roller with a groove along its edge for holding a belt, rope or cable. When hung between two supports with a belt, rope or cable, one or more sheaves make up a pulley. The words sheave and pulley are sometimes used interchangeably.

Pulley block with a sheave