A caliper is a precision measuring tool with two jaws or legs used to measure the internal/external dimensions (length, diameter, thickness, depth) of objects, common in engineering, woodworking and medicine, but “caliper” also refers to the part of a vehicle’s brake system that squeezes pads onto a rotor for stopping. Measuring calipers come in types like vernier (with scales) or digital (with electronic readouts) for high accuracy, while brake calipers are crucial for vehicle safety.