noun

• The act of varying; a partial change in the form, position, state, or qualities of a thing.
• A related but distinct thing.
• (nautical) The angular difference at the vessel between the direction of true north and magnetic north.
• (board games) A line of play that differs from the original.
• (music) 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.
• (genetics) The modification of a hereditary trait.
• (astronomy) Deviation from the mean orbit of a heavenly body.