The property of an antenna that defines the range of frequencies to which it will respond, is called its:

Bandwidth is the standard radio term for the range of frequencies over which an antenna, or any electronic circuit, operates effectively. For antennas, this is typically the frequency range where the Standing Wave Ratio (SWR) remains at an acceptable level, such as under 2:1. Distractors like 'beamwidth' and 'front-to-back ratio' relate to the physical shape and direction of the radiated signal, not its frequency. 'Antenna aperture' refers to an antenna's effective area for capturing radio waves. Understanding the difference between the spatial properties of the signal and the frequency properties of the antenna is crucial for selecting the right antenna for your needs.