Basic Category Theory
《Basic Category Theory》 · 第 41 页 · Definition 2.1.1
If there is a natural bijection \(\mathcal B(F(A),B)\cong\mathcal A(A,G(B))\), then \(F\) is left adjoint to \(G\), \(G\) is right adjoint to \(F\), and \(F,G\) are adjoint functors.