Calipers
Terminology

Caliper is the American spelling, while calliper (double "L") is the British spelling.

A single tool might be referred to as a caliper or as calipers — a plural only (plurale tantum) form, like scissors or glasses.

Colloquially, the phrase "pair of verniers" or just "vernier" might refer to a vernier caliper. In loose colloquial usage, these phrases may also refer to other kinds of calipers, although they involve no vernier scale. In machine-shop usage, the term "caliper" is often used in contradistinction to micrometer, even though outside micrometers are technically a form of caliper. In this usage, caliper implies only the form factor of the instrument.
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