Jimmy won't start, it just clicks

I have a 1996 gmc jimmy SLS 4x4. The other day I went to start her up and it won't turn over or even try too. When I put the key in and turn it the battery turns on, lights work, radio, but when u turn the key to start it, it just clicks once then nothing. It won't try to crank itself over. I can hear the fuel pump priming the engine and the starter just clicks once and then that's it. Any suggestion on what it could be?