What is the term for the frequency at which the grounded-base current gain of a bipolar junction transistor has decreased to 0.7 of the gain obtainable at 1 kHz?

In bipolar junction transistor (BJT) terminology, the current gain in a common-base (grounded-base) configuration is designated by the Greek letter alpha. As the operating frequency increases, this gain begins to drop off due to the physical limitations of charge carrier transit times. The frequency at which the alpha gain drops to 0.7 (more precisely 0.707, representing the half-power point or -3 dB) of its low-frequency value is known as the alpha cutoff frequency. The distractor 'beta cutoff frequency' applies to the common-emitter configuration, where current gain is designated by beta. Remembering that 'grounded-base' relates to 'alpha' and 'grounded-emitter' relates to 'beta' is the key to getting this right.