Most terms I've been using I've explained within the text, but it's nice to have a separate reference.  For a fantastic site with tons and tons of techie acronyms and terms explained in detail, go to Whatis.com.  I'll be adding to this section whenever I feel like retyping a bunch of stuff.

Adapter - The card that connects all your SCSI devices with the rest of your computer.

Bus - The entire string of SCSI devices including the controller

Byte - 8 bits

Channel - An independent path for electrical signals

HVD (High Voltage Differential) - An old and expensive way of extending the bus.

LVD (Low Voltage Differential) - The newest way to extend the bus.  Costs only slightly more than SE.

SCA (Single Connector Attachment) - An 80 pin plug that combines SCSI signals, power, and other signals.

Arbitration - This is the negotiation between devices on the bus.  Control of the bus is determined in this phase.

Domain Validation - When the SCSI bus is reset (such as when you boot your computer) the controller polls each device to determine how to communicate with it.  What Domain Validation does is to actually test these settings to make sure the device will work properly.  If not, the controller will then renegotiate with the device, trying a less demanding (slower) communications rate.

CRC (Cyclic Redundancy Check) - An error-checking procedure available in Ultra3 (and used in Ultra160) that checks the data sent and the data received to make sure they match.

Packetized SCSI - Converts slower arbitration phases to more data transfer-like phases.  This won't be really necessary until transfer rates hit 320MB/s.

QAS (Quick Arbitration and Select) - Reduces the time needed for the arbitration phase, which occurrs when control of the bus changes betweeen two devices.

Double Transition Clocking - A method of transferring data on both the rising and falling edge of a signal.  It is used only during the data transferral stage.  This is how Ultra160 devices can transfer 160MB/s; 40MHz x 2 bytes x 2 transfers per cycle = 160 MB/s.

Fast-80 - The transfer method that uses Double Transition Clocking.  It should be noted that Fast-80 and DTC always go hand-in-hand.