Calipers

A caliper (British spelling also calliper, or in plurale tantum sense a pair of calipers) is a device used to measure the distance between two opposite sides of an object. A caliper can be as simple as a compass with inward or outward-facing points. The tips of the caliper are adjusted to fit across the points to be measured, the caliper is then removed and the distance read by measuring between the tips with a measuring tool, such as a ruler.

It is used in many fields such as mechanical engineering, metalworking, forestry, woodworking, science and medicine.

Nomenclature variants

A plurale tantum sense of the word "calipers" coexists in natural usage with the regular noun sense of "caliper". That is, sometimes a caliper is treated cognitively like a pair of glasses or a pair of scissors, resulting in a phrase such as "hand me those calipers" or "those calipers are mine" in reference to one unit.

Also existing colloquially but not in formal usage is referring to a vernier caliper as a "vernier" or a "pair of verniers". In imprecise colloquial usage, some speakers extend this even to dial calipers, although they involve no vernier scale.