Bündel

Bündel is a German noun meaning a bundle, a group of objects bound or tied together. In everyday language it refers to physical collections such as a bundle of sticks, a sheaf of papers, or a bundle of cables, typically held together by string, rope, or wire, and used for easier handling, transport, or storage. The term conveys the notion of treating multiple items as a single unit.

In specialized contexts the word is used similarly to the English term bundle. In mathematics and theoretical physics, Bündel is the standard German term for fiber bundles, including vector bundles and principal bundles. A fiber bundle consists of a base space, a total space, a fiber, and a projection, with a local product structure that may twist globally. Notable examples include the tangent bundle of a manifold or the Möbius strip viewed as a nontrivial line bundle.

Etymology: Bündel derives from a root related to binding, connected with the German verb binden (to bind) and the concept of gathering items together. Related forms include Bündelung (the act of bundling) and bündig (flush or closely fitting), though the latter has separate origins.

See also: Bundling, fiber bundle, vector bundle.