The width or capacity of a communications channel.

Analog bandwidth is measured in Hertz (Hz) or cycles per second. The actual bandwidth size is the difference between the lowest and highest frequency in the band, which determines how much information can be transmitted at once.

Digital bandwidth is the amount or volume of data that may be sent through a channel, measured in bits per second, without distortion.

Bandwidth should not be confused with the term band, such as a wireless phone that operates on the 800 MHz band. Bandwidth is the space it occupies on that band.

The relative importance of bandwidth in wireless communications is that the size, or bandwidth, of a channel will impact transmission speed. Lots of data flowing through a narrow channel takes longer than the same amount of data flowing through a broader channel.