What do they "degenerate"?

From: Norm Dresner (ndrez_at_att.net)
Date: 06/28/04 

Date: Mon, 28 Jun 2004 18:57:51 GMT

I'm a mathematical physicist/computer scientist, not an EE and elementary
electronics books are not in my library nor in my past. I've run across
terms like "emitter degeneration resistor" several times in a discussion of
amplifier circuits and I've seen that they're resistors added to a circuit
between the (in this particular case) transistor's emitter and a load or
supply rail. What do they "degenerate?"

TIA
    Norm