Quarterturn

A quarter-turn is a unit of angular displacement equal to one quarter of a full rotation. It corresponds to 90 degrees, or pi/2 radians. Four quarter-turns make a complete 360-degree rotation.

The term is widely used to describe the amount of rotation produced by a mechanism, control, or orientation in engineering, design, and everyday devices. Quarter-turns imply a discrete, easily repeatable motion, often used when a simple, quick change of state is desired. In practice, a 90-degree turn can open or close a valve, latch a mechanism, or switch a device from one position to another.

Common applications include quarter-turn valves, which control fluid flow with a 90-degree rotation of the valve stem; knobs, levers, and locking mechanisms that operate after a quarter-turn; and piping or plumbing contexts where rapid operation is valued. In these contexts, the direction of rotation (clockwise or counterclockwise) is often specified to avoid ambiguity.

In games and puzzles, quarter-turn moves are a standard unit of rotation. For example, many twisty puzzles and the Rubik’s Cube use quarter-turns (90-degree moves) and their multiples as fundamental operations. In computer graphics and mathematics, quarter-turns are used to describe rotations about a principal axis by 90 degrees, mapping angle θ to θ + 90 degrees.

Overall, a quarter-turn is a simple, widely understood rotation unit that facilitates precise, repeatable control of mechanical and geometric configurations.