2.1 of the ITU Radio Regulations defines the following nomenclature:

The radio spectrum shall be subdivided into nine frequency bands, which shall be designated by progressive whole numbers in accordance with the following table. As the unit of frequency is the hertz (Hz), frequencies shall be expressed:

• in kilohertz (kHz), up to and including 3 000 kHz;
• in megahertz (MHz), above 3 MHz, up to and including 3 000 MHz;
• in gigahertz (GHz), above 3 GHz, up to and including 3 000 GHz.However, where adherence to these provisions would introduce serious difficulties, for example in connection with the notification and registration of frequencies, the lists of frequencies and related matters, reasonable departures may be made.
  

  Bandnumber	Symbols	Frequency range (lower limit exclusive, upper limit inclusive)	Corresponding metric subdivision	Metric abbreviations for the bands
  4	VLF	3 to 30 kHz	Myriametric waves	B.Mam
  5	LF	30 to 300 kHz	Kilometric waves	B.km
  6	MF	300 to 3 000 kHz	Hectometric waves	B.hm
  7	HF	3 to 30 MHz	Decametric waves	B.dam
  8	VHF	30 to 300 MHz	Metric waves	B.m
  9	UHF	300 to 3 000 MHz	Decimetric waves	B.dm
  10	SHF	3 to 30 GHz	Centimetric waves	B.cm
  11	EHF	30 to 300 GHz	Millimetric waves	B.mm
  12		300 to 3 000 GHz	Decimillimetric waves	N.mm

  NOTE 1: “Band N” (N = band number) extends from 0.3 × 10^N Hz to 3 × 10^N Hz.
  NOTE 2: Prefix: k = kilo (10³), M = mega (10⁶), G = giga (10⁹).