IEC 60050-617:2009 has been published as a consequence of deregulation of the electricity market, it appeared necessary to establish a common glossary with those terms defining actors in the market, interface between actors and the technical or financial terms having a specific meaning in the context of electricity market. This horizontal standard IEC 60050-617:2009 is primarily intended for use by technical committees in the preparation of standards in accordance with the principles laid down in IEC Guide 108. One of the responsibilities of a technical committee is, wherever applicable, to make use of horizontal standards in the preparation of its publications. The contents of this horizontal standard will not apply unless specifically referred to or included in the relevant publications. The content of 60050-617 will be freely available at www.electropedia.org. Electropedia (also known as the IEV Online) is the world's most comprehensive online electrical and electronic terminology database containing more than 20 000 terms and definitions.