This document defines technical terms associated with wireless enhanced 9-1-1 (E 9-1-1) systems, which automatically provide emergency response dispatchers with call data and location information of wireless 9-1-1 calls in local government communications centers. One of two online supplements to "Wireless E 9-1-1," by Colin Haller, IQ Report 36, no. 3 (Washington, D.C.: ICMA, 2004).