1. The range of frequencies over which a given device is designed to operate within specified limits.
2. The differences between half-power points, i.e., the frequencies at which the power drops to half the peak power (3 dB).
3. The effective bandwidth is
where is the power at the frequency and is the maximum power. It is the width of a boxcar with the same total power and the same peak power.
4. The rate at which a computer resource can carry (accept or deliver) data. Usually expressed in bytes per second or bits per second.