So you want to give an equation a name in LaTeX, instead of the number it gets automatically… For some reason, Google will resist telling you how. You may be tempted to use the eqname package. No need! No need at all! Use the \tag command. Why isn’t this easier to figure out?
UPDATE: I apologize to the writers of the amsmath documentation, who mention this pretty much immediately after they introduce the concept of equation numbering. I always assume that Google can find these things for me.
Procrastiblog 
Thank you so much man you just ended 30 minutes of infructuous search on google…
Comment by Flo — April 19, 2008 @ 5:09 pm
…but it doesn’t work with eqnarray…
Comment by Flo — April 19, 2008 @ 5:14 pm
flo, eqnarray has been deprecated in favor of align. And \tag does work with align. See the amsmath documentation.
Also, thanks for “infructuous.” I hadn’t heard that one before!
Comment by Chris — April 23, 2008 @ 3:37 pm