The antenna definitions standard [1] currently has no terms that describe antenna performance in the time domain, possibly due to the complexity of the equations. However, if the antenna equations are expressed using quantities related to the square root of power, then simple expressions are obtained that are valid in both the frequency and time domains. This leads to a number of new terms that should be considered for inclusion in the next revision of the standard. Doing so would provide a common language for discussing antenna performance in the time domain. It would also add phase information to common frequency-domain terms, such as antenna gain and radar cross section.