Hurewicz homomorphism
= Hurewicz homomorphism
{c}
{title2=$h_n:\pi_n(X)\to H_n(X;\mathbb Z)$}
A sphere map $f:S^n\to X$ is sent to $f_*[S^n]\in H_n(X;\mathbb Z)$. After tensoring with $\mathbb Q$ this gives the rational <Hurewicz homomorphism>. It is natural in $X$, sends <Whitehead products> to zero, and is an isomorphism in the first nonzero <homotopy> degree of a <simply connected> space by the <Hurewicz theorem>.