Spectrum – or radio spectrum – is the range of electromagnetic radio frequencies used to transmit signals wirelessly. Radio frequencies are allocated for different types of use: radio, television, mobile telecommunications, Wi-Fi and some specific communications e.g. wireless microphones, satellites, radars or the military. The frequencies range from 9 kilohertz (kHz) to 3000 gigahertz (GHz).
Spectrum is split into different parts that are then allocated to one or more services (shared spectrum). Each of these services is typically licensed for use by one or more operators (e.g. broadcasting companies or mobile network operators that transmit in a given piece of spectrum).