Loop (topology)

In mathematics, a loop in a topological space X is a continuous function f from the unit interval I = [0,1] to X such that f(0) = f(1). In other words, it is a path whose initial point is equal to its terminal point. A loop may also be seen as a continuous map f from the pointed unit circle S^1 into X, because S^1 may be regarded as a quotient of I under the identification of 0 with 1. The set of all loops in X forms a space called the loop space of X.