FOREWORDDefinitions of terms in the field of antennas are provided.This document is a revision of IEEE Std 145-1983@ IEEE Standard Definitions of Terms for Antennas@ and corrects minor errors that appeared in that printing. The original standard was issued in 1969.ScopeIt 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 that includes an antenna. Examples of such cases are an adaptive antenna system and a signal-processing 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. For those in which phase or polarization is a significant part of the definition@ a coherent source of power is implied. Whenever a term is commonly used in other fields but has specialized significance in the field of antennas@ this is noted in the title.When applying terms pertaining to radiation characteristics@ such as gain@ polarization@ beamwidth@ etc.@ to multiple-beam antennas@ each port shall be considered to be that of a separate antenna with a single main beam. For polarization diversity systems that may include active devices@ these terms apply to each polarization state for which the antenna is adjusted.Throughout this standard@ where phasors are used@ or are implied@ the time convention shall be taken to be exp(j??).