(1):

(n.) Extent to which a thing varies; amount of departure from a position or state; amount or rate of change.

(2):

(n.) One of the different arrangements which can be made of any number of quantities taking a certain number of them together.

(3):

(n.) Repetition of a theme or melody with fanciful embellishments or modifications, in time, tune, or harmony, or sometimes change of key; the presentation of a musical thought in new and varied aspects, yet so that the essential features of the original shall still preserve their identity.

(4):

(n.) The act of varying; a partial change in the form, position, state, or qualities of a thing; modification; alternation; mutation; diversity; deviation; as, a variation of color in different lights; a variation in size; variation of language.

(5):

(n.) Change of termination of words, as in declension, conjugation, derivation, etc.