Forward and Reverse-active in Bipolar Junction Transistor:

Forward-active (or simply, active):

The base-collector junction is reverse biased and base-emitter junction is forward biased. Several bipolar transistors are planned to afford the greatest common-emitter current gain, β_F, in forward-active mode. If this is the case, the collector-emitter current is almost proportional to the base current, however many times larger, for small base current variations.

Reverse-active (or inverse-active or inverted):

By reversing the biasing situations of the forward-active region, a bipolar transistor departs into reverse-active mode. In this form, the emitter and collector regions switch roles. Since most BJTs are planned to maximize current gain in forward-active mode, the β_F in inverted mode is many (2-3 for the ordinary germanium transistor) times smaller. This transistor mode is used rarely, generally being considered only for failsafe conditions and some sorts of bipolar logic. To the base reverse bias breakdown voltage might be an order of magnitude lower in this type of region.