Calliper is described as a measuring device with moving parts that come together to determine the dimensions of a part. In their simplest, traditional, form they can be used for both inside and outside measurements.
In their modern form the hinge is sprung and the arms are connected Midway by an adjustable screw. In this form inside and outside callipers are separate devices.
Most bicycle brakes use a similar mechanism to move the brake shoes inward toward the rim, so they are called calliper brakes. A calliper brake uses a single assembly to move both brake shoes together, unlike a cantilever brake that has a separate unit on each side of the rim.
A brake calliper attaches to the bicycle by a single bolt, through the centre of the fork crown or the brake bridge on the seat stays.
List of books: Calliper