This standard is a comprehensive revision and extension of the previous Standard Definitions of Terms of Antennas. It is assumed in this standard that an antenna is a passive linear reciprocal device. Thus@ where a definition implies the use of an antenna in a transmitting situation@ its use in a receiving situation is also implicit unless specifically stated otherwise. When an antenna or group of antennas is combined with circuit elements that are active@ nonlinear@ or nonreciprocal@ the combination is regarded as a system which includes an antenna. Examples of such cases are an adaptive antenna system and a signalprocessing antenna system; the complete conical- scanning@ monopulse@ and compound interferometer systems also fall in this category. For terms that are quantitative it is understood that frequency must be specified. Those terms in which phase or polarization is a significant part of the definition imply a coherent source of power. Whenever a term is commonly used in other fields but has specialized significance in the field of antennas@ this is noted in the title.