Reciprocal length

Reciprocal length or inverse length is a quantity or measurement used in several branches of science and mathematics, defined as the reciprocal of length.

Common units used for this measurement include the reciprocal metre or inverse metre (symbol: m⁻¹), the reciprocal centimetre or inverse centimetre (symbol: cm⁻¹). In optics, the dioptre is a unit equivalent to reciprocal metre.