The act, process, or result of varying. The state or fact of being varied. See Synonyms at difference. The extent or degree to which something varies: a variation of ten pounds in weight. Magnetic declination. Something slightly different from another of the same type. Biology Marked difference or deviation from the normal or recognized form, function, or structure. Biology An organism or plant exhibiting such difference or deviation. Mathematics A function that relates the values of one variable to those of other variables. Music A form that is an altered version of a given theme, diverging from it by melodic ornamentation and by changes in harmony, rhythm, or key. Music One of a series of forms based on a single theme. A solo dance, especially one forming part of a larger work.