Fjær

Fjær is a Norwegian noun with two primary meanings: a feather and a spring. As a feather, fjær denotes the light, keratinous structure that grows from a bird's skin and constitutes the bird's plumage. A feather has a hollow calamus that anchors in a follicle, a central rachis or shaft, and paired vanes composed of barbs and barbules that interlock to form a flat surface. Feathers are categorized as down feathers for insulation, contour feathers that shape the body, and flight feathers on the wings and tail that provide lift and steering. Birds grow and molt their feathers periodically, replacing worn plumage. Coloration arises from pigments such as melanin or from structural colors produced by microstructures.

In a second sense, fjær also means a mechanical spring. A spring is an elastic element that stores energy when deflected and returns it when released. Common types include coil springs (compression and extension), leaf springs, and torsion springs. They are typically made of metal alloys or polymers and are described by a stiffness constant k, following Hooke's law F = -kx. Springs are used in countless devices, including vehicle suspensions, clocks and watches, pens, and industrial machinery. Their design focuses on fatigue resistance and the range of motion required.

The dual meaning of fjær reflects its central idea of something that can be extended or stretched and then return to a resting state, whether in living organisms or engineered systems.