A caliper is a seven-letter thickness-measuring instrument used to measure the distance between two opposite sides of an object. It is commonly used in engineering and machining to measure the thickness of a material, such as a sheet of metal or paper. Calipers can also be used to measure the diameter of a round object, such as a pipe or a cylinder. The caliper is composed of two arms that are connected by a hinge, and the arms are equipped with a measuring scale. The caliper is placed around the object and the arms are adjusted until they touch both sides of the object. The distance between the two arms is then read from the scale.