Vā'ri-ā'tion, n.

n. [Fr. variation, Pr. variacio, Sp. variacion, It. variazione, Lat. variatio.] 1. The act of varying; a partial change in the form, position, state, or qualities of the same thing; alteration; mutation; diversity; as, a variation of color in different lights; a variation in the size of a plant from day to day; variation of language. The essences of things are conceived not capable of such variation. Locke. In some other places, are born more females than males; which, upon this variation of proportion, I recommend to the curious. Graunt.

2. The extent to which a thing varies; the degree or amount of departure from a former position or state; amount or rate of change.
3. (Gram.) Change of termination of words, as in declension, conjugation, derivation, and the like.
4. (Mus.) Repetition of a tune or melody with various embellishments and fanciful changes.

Annual variation (Astron.), the yearly change in the right ascension or declination of a star, produced by the combined effects of the precession of the equinoxes and the proper motion of the star.—Calculus of variations. See CALCULUS.—Variation compass, a compass constructed especially for measuring the variation of the needle.—Variation of the moon (Astron.), an inequality of the moon’s motion, depending on the angular distance of the moon from the sun. It is greater at the octants, and zero at the quadratures.—Variation of the needle (Geog. & Nav.), the angle included between the true and magnetic meridians of a place; the deviation of the direction of a magnetic needle from the true north or south points of the horizon;—called also declination of the needle. Syn.—Change; vicissitude; variety; mutation; deviation.