end (圈)
$ \int_C F(C,C),$ \int_{\bf C}F
圈$ \bf C,$ \bf Xと對象$ X\in|{\bf X}|と雙函手$ F:{\bf C}^{\rm op}\times{\bf C}\to{\bf X}による楔 (wedge)$ w:X\ddot\to Fの內で普遍 (圈論)的なものを言ふ 射$ p_C:\int_C F(C,C)\to F(C,C)を end (圈)の射影 (projection) と言ふ 射$ F(C,C)\to F(C,C')と射$ F(C',C')\to F(C,C')との圖式$ \int_C F(C,C)\to\prod_{C\in|{\bf C}|}F(C,C)\rightrightarrows\prod_{C\to C'}F(C,C')の等化子になる