oh of) fn. A computer science notation for describing the computational complexity of an algorithm in shorthand. Many algorithms are O(n), meaning they require a number of CPU cycles in proportion to the number, n, of data elements to be manipulated. For example, algorithms that require 2n + 4 and 45n + 340, respectively, are both O(n). Any algorithm that is polynomial in nature is O(nd) where d is the degree of the polynomial. Many algorithms are O(log2 n), O(ln n), or O(n2); others, by contrast, are NP-incomplete.