variation

Usually The act of varying; a partial change in the form, position, state, or qualities of a thing.

Usually A related but distinct thing.

Nautical, Transport Usually The angular difference at the vessel between the direction of true north and magnetic north.

Usually A line of play that differs from the original.

Entertainment, Lifestyle, Music Usually A technique where material is repeated with alterations to the melody, harmony, rhythm, timbre, texture, counterpoint or orchestration; but with some invariant characteristic, e.g. a ground bass.

Biology, Genetics, Medicine, Natural sciences, Sciences Usually The modification of a hereditary trait.

Astronomy, Natural sciences Usually Deviation from the mean orbit of a heavenly body.

Human sciences, Linguistics, Sciences Usually The situation where two or more linguistic forms appear in the same environment without a change in meaning, the choice of form being determined by factors of dialect, sociolect, register or simply the speaker's preference.

Mathematics, Sciences Usually An infinitesimal perturbation applied to a function, typically denoted δf, used to probe how a functional changes.

Mathematics, Sciences Usually The corresponding first-order change in a functional induced by such a perturbation, typically denoted δJ[f] and called the first variation.