Categories for the Working Mathematician
《Categories for the Working Mathematician》 · 第 62—63 页 · Chapter III, Section 3
A coproduct of \(a\) and \(b\) is an object \(a+b\) with arrows \(i:a\to a+b\), \(j:b\to a+b\) such that every pair \(f:a\to c\), \(g:b\to c\) factors uniquely through \(a+b\).