  Fractional variation is defined as the limit of the difference quotient of
the increments of a function and its argument raised to a fractional power.
Fractional velocity can be suitable for characterizing singular behavior of
derivatives of H\"olderian functions and non differentiable functions. The
manuscript derives the product rules for fractional variation. Correspondence
with integer-order derivatives is discussed. It is demonstrated that for
H\"older functions under certain conditions the product rules deviates from the
Leibniz rule. This deviation is expressed by another quantity, fractional
co-variation. Basic algebraic properties of the fractional co-variation are
demonstrated.
