The symbol O(x), pronounced "big-O of x, " is one of the Landau symbols and is used to symbolically express the asymptotic behavior of a given function. In particular, if n is an integer variable which tends to infinity and x is a continuous variable tending to some limit, if ϕ(n) and ϕ(x) are positive functions, and if f(n) and f(x) are arbitrary functions, then it is said that f element O(ϕ) provided that left bracketing bar f right bracketing bar