Sometimes it is necessary to be able to refer to subexpressions of an equation. In order to do that these subexpressions should be numbered. In standard LaTeX there is no provision for this. To solve this problem Stephen Gildea once wrote subeqn.sty for LaTeX 2.09; Donald Arsenau rewrote the macros and Johannes Braams made them available for LaTeX2e.

Note that this package is not compatible with the package subeqnarray, written by Johannes Braams.

This package can be used together with the LaTeX options leqno and fleqn. The authors are Donald Arseneau and Johannes L. Braams. See also subeqnarray.