snúningur

Snúningur is the Icelandic term for rotation or spin, referring to the motion of an object turning around an axis. In everyday language it also denotes a turn of a knob or handle on a device. The noun derives from the verb snúa, to turn, with the agentive suffix -ingur forming snúningur as the act or result of turning.

In physics and mathematics, snúningur denotes angular motion about an axis. The rate of rotation is called angular velocity, denoted by ω, and is measured in radians per second. The orientation of a rotating body is described by a rotation vector or matrix; the right-hand rule gives the direction of ω. Linear velocity and rotational motion are related by v = ω × r, and the angular momentum L = Iω with the torque τ = dL/dt. A rotating rigid body has a moment of inertia I that depends on mass distribution and geometry.

Earth’s daily snúningur refers to its rotation about its axis, approximately one sidereal day, which governs the cycle of day and night. In engineering and technology, snúningar occur in gears, rotors and other rotating machinery, as well as in everyday devices such as knobs and dials. The term is also used in astronomy and biomechanics to describe rotation in celestial bodies and joints, respectively.

Overall, snúningur covers both the physical phenomenon of rotation and common usage for turning actions, and it forms a basic concept in physics, engineering and everyday language in Icelandic.