Chain homotopy
= Chain homotopy
{wiki}
= Chain homotopic
{synonym}
Chain maps $f,g:C\to C'$ are chain homotopic when there are maps $h_i:C_i\to C'_{i+1}$ such that
$$
f_i-g_i=d'_{i+1}h_i+h_{i-1}d_i.
$$
Chain-homotopic maps induce the same map on homology.