In topology, a branch of mathematics, for i ≥ 2 {\displaystyle i\geq 2}, the i-th homotopy group with coefficients in an abelian group G of a based space X is the pointed set of homotopy classes of based maps from the Moore space of type {\displaystyle } to X, and is denoted by π i {\displaystyle \pi _{i}}. Wikipedia