A specification of semiconductor diodes. Recovery rate (trr) is the amount of time needed for a diode to switch from on (forward bias) to off (reverse bias), or vice versa after the voltage has switched direction. General purpose diodes have a recovery rate of about a microsecond, while Schottky diodes usually have recovery rates of around a nanosecond.
The faster the recovery rate, the higher a frequency the diode can effectively handle. Recovery rate is not a concern below the radio frequencies, because even the lowest quality diodes have a recovery rate no more than a few microseconds.