Core: Central element, usually of fiber or steel, of a single layer stranded rope, around which are laid helically the outer strands of a stranded rope or the outer unit ropes of a cable-laid rope.

Fiber core: Core made from either natural (e.g. hemp, sisal) or synthetic fibers (e.g. polypropylene) and designated by its diameter and runnage.

Steel core: Core produced either as an independent wire rope (e.g. 7x7) or wire strand (e.g. 1x7).

Solid polymer core: Core produced as a single element of solid polymer having a round or grooved shape. It may also contain internal elements of wire or fiber.

Insert: Element of fiber or solid polymer so positioned as to separate adjacent strands or wires in the same or overlying layers and fill, or partly fill, some of the interstices in the rope.