stereochemistry (stÄr'Ä-Å-kÄm'Ä­-strÄ) The branch of chemistry that deals with the spatial arrangements of atoms in molecules and with the chemical and physical effects of these arrangements.
ECU. Short for Electronic Control Unit, the ECU is a name given to a device that controls one or more electrical systems in a vehicle. It operates much like the BIOS does in a computer.
The engine control unit / module (ECM, ECU, or PCM) uses the information that is sent to it from the throttle position sensor, along with input from other sensors, to calculate engine load and control many things such as fuel and ignition timing, as well as automatic transmission shift points.