Tidal locking settles a body's spin into a sustained relation with its orbital motion through tidal forces and tidal dissipation. The simplest case is synchronous rotation, a spin-orbit resonance. On an ideal circular orbit, with spin axis perpendicular to the orbital plane, the body keeps the same face toward its companion, as the Moon approximately does toward Earth. [ref].
This article retains the broader sense of tidal locking as capture into a spin-orbit resonance; the term is also commonly used specifically for synchronous rotation. Tidally evolved rotation need not be : Mercury has a spin-orbit resonance with the Sun, turning three times in two orbital periods. The distinction matters when inferring illumination or climate from a spin period. [ref].
Tidal locking is a phenomenon that occurs when an astronomical body, such as a moon or a planet, rotates on its axis in such a way that the same side always faces the body it is orbiting. This happens due to gravitational interactions between the two bodies, which create tidal forces that distort their shapes. In the case of a tidally locked moon, its orbital period around the planet matches its rotation period.
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