This document, Glossary, is the first in a series of reports to identify, describe, and apply techniques for analyzing the impacts of certain electric utility concepts. This report was developed with a focus on the currently evolving issues of ratemaking, especially as they might be expected to arise under Sections 101, 111, 113, 114, 131, 132, and 210 of the P.U.R.P.A. of 1978. Because the evolutionary process of ratemaking has led to multiple proceedings and changes of inference in some terms, the glossary attempts to delineate these changes where appropriate. Definitions not uniquely related to ratemaking are included if they are likely to be used in ratemaking proceedings. To avoid unnecessary duplication of effort and expense, the compilers relied heavily on previously developed, publicly available glossaries and definitions developed by organizations such as Edison Electric Institute, the Electric Power Research Institute, and the Institute of Electrical and Electronics Engineers. Existing definitions were revised and new ones were developed as appropriate.