variation

noun

1. The act of varying; a partial change in the form, position, state, or qualities of a thing.
2. A related but distinct thing.
3. The angular difference at the vessel between the direction of true north and magnetic north.
4. A line of play that differs from the original.
5. 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.
6. The modification of a hereditary trait.
7. Deviation from the mean orbit of a heavenly body.
8. 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.
9. An infinitesimal perturbation applied to a function, typically denoted δf, used to probe how a functional changes.
10. The corresponding first-order change in a functional induced by such a perturbation, typically denoted δJ[f] and called the first variation.