Base

1-The electrode of a bipolar transistor between the emitter and the collector. Controlling a small flow of electrons moving into or out of the base controls a much larger flow of electrons between the emitter and the collector. The base of a transistor compares with the grid of a vacuum tube. 

2-A place used as a centre of operations ; a headquarters. 

3-The lowest part or edge of something, especially the part on which it rests or is supported.