2002 Ford Focus Jumped my car yesterday it was fine, won't

I had to jump my 2002 Ford Focus yesterday, and it was fine the rest of the day. It started three separate times.

Then early this morning, my wife went out to see if it would start up (in case she needed to make alternate plans to get to work). It started up fine. So she went out a half an hour later to start it and warm the car, but it wouldn't start.

We tried to jump it, but it wouldn't start. The radio came on, it clicked, but the engine wouldn't start.

I'm just not sure what it is, since it jumped fine yesterday and held a charge, then started once this morning.