Notation for comparing the relative order of functions. We write f(x) = o(g(x)) if f(x)/g(x) approaches 0 as x→∞, so, for example, (x + 1)(x + 2) = o(x³). The notation is also used in the neighbourhood of finite values; for example, sinx = x + o(x²) denotes the fact that (sinx − x)/x² approaches 0 as x→0. Compare big O notation.