Transition band
![A plot of the frequency response of a Butterworth Lowpass filter, with a cutoff frequency of 2kHz.](/Images/godic/202502/17/Butterworth_lowpass5551.png")
The transition band, also called the skirt, is a range of frequencies, that allows a transition between a passband and a stopband of a signal processing filter. The transition band is defined by a passband and a stopband cutoff frequency or corner frequency.