Turning is a machining process in which a cutting tool, usually a non-rotating tool bit, describes the spiral path of the tool, moving approximately linearly while the workpiece is rotating.

Turning can be done manually, in the traditional form of a lathe, which often requires continuous operator supervision, or using an automatic lathe. Nowadays the most common type of such automation is computer numerical control, better known as CNC.

During turning, the workpiece (a piece of relatively rigid material such as wood, metal, plastic or stone) is rotated and the cutting tool is moved along 1, 2 or 3 axes of motion in order to obtain precise diameters and depths. The rotation can take place on the outside of the cylinder or on the inside of the cylinder in order to obtain tubular elements with different geometries. Although now quite rare, early lathes can even be used to produce complex geometric figures, even platonic solids.