Smash product of CW pairs
= Smash product of CW pairs
{title2=$(X,A)\wedge(Y,B)=(X\times Y,(A\times Y)\cup(X\times B))$}
The quotient of the displayed <CW pair> is $(X/A)\wedge(Y/B)$. In a multiplicative <generalized cohomology theory>, external products of relative classes of degrees $k,m$ take values in degree $k+m$ of this pair. Pullback along a diagonal produces the <relative cup product>.