 In the Methodus fluxionum Newton makes explicit his conception of variable quantities as generated by motions, and introduces his characteristic notation. He calls the quantity generated by a motion a fluent, and its rate of generation a fluxion. The fluxion of a fluent \(x\) is denoted by \(\dot{x}\), and its moment, or “infinitely small increment accruing in an infinitely short time \(o\)”, by \(\dot{x} o\). The problem of determining a tangent to a curve is transformed into the problem of finding the relationship between the fluxions \(\dot{x}\) and \(\dot{z}\) when presented with an equation representing the relationship between the fluents \(x\) and \(z\). (A quadrature is the inverse problem, that of determining the fluents when the fluxions are given.) Thus, for example, in the case of the fluent \(z = x^n\), Newton first forms \(\dot{z} + \dot{z} o = (\dot{x} + \dot{x} o)^n\), expands the right-hand side using the binomial theorem, subtracts \(z = x^n\), divides through by \(o\), neglects all terms still containing \(o\), and so obtains \(\dot{z} = nx^{n-1} \dot{x}\).