Ausdehnen

Ausdehnen is a German verb meaning to extend, stretch, widen, or dilate something. The related noun Ausdehnung denotes the act or result of expansion and the extent of something. The word derives from aus- (“out”) and dehnen (“to stretch”). In everyday language, ausdehnen can refer to extending a physical object, stretching a body part, or enlarging an area.

In physics, Ausdehnung describes a change in size with external conditions. Thermal expansion is the best-known example: most materials expand when heated, with a linear expansion described by ΔL = αL0ΔT and a volumetric expansion described by ΔV/V0 ≈ βΔT, where α and β are material coefficients. In cosmology, Ausdehnung also denotes the expansion of space itself, described by a growing scale factor a(t) and observed as the recession of distant galaxies (Hubble’s law).

In biology and medicine, Ausdehnung (or Dilatation) refers to the widening or dilation of hollow structures, such as blood vessels, the pupil, or the cervix during childbirth. In everyday use, the term covers activities like muscle stretching, extending a rope, or increasing the spatial reach of a region or organization.

Related concepts include the antonym Verengen (constriction) and terms for specific types of expansion, such as Thermalausdehnung (thermal expansion) and cosmologische Ausdehnung (cosmological expansion).