From Longman Business Dictionary
variationvar·i·a·tion /ˌveəriˈeɪʃənˌver-/ noun [countableC, uncountableU] a difference or change in the normal amount or appearance of somethingLabor figures in both reports are adjusted for seasonal variation (=variation that depends on the time of year).
variation onThey are using the same advertising campaign, with just a variation on the original slogan.