Therefore, instead of defining it as the coefficient of the first term of the development (for a term is designated as the first with reference to the others that follow it in the series, but any such power as that of an increment, like the series itself, has no place here), the plain expression, 'derived function of a power,' or the just said, 'function of the raising of a magnitude to a power,' would be preferable; these are expressions which presuppose that the derivation is a development falling within a power.