In a bipolar transistor, the change of collector current with respect to base current is called:

The term "beta", also known as hFE, describes the forward current gain of a bipolar junction transistor in a common emitter configuration. It is mathematically the ratio of the change in collector current to the change in base current. Since a very small change in base current results in a large change in collector current, beta values are typically much greater than 1, often ranging from 50 to over 200. This distinguishes it from "alpha," which is the ratio of collector current to emitter current.