What should I name my base class?

I know this probably doesn't matter, but what is the pretty standard naming convention for base class names? Should I name it "base.class", "main.class", or the name of my application, "application.class"? What does everyone else use? If I went by the pear standards, they use a base class name of "pear.php" so I probably would go with "application.class" or "application.php" Thanks, Brent