Sideband

Sideband: In amplitude modulation (AM), a band of frequencies higher than or lower than the carrier frequency, containing energy as a result of the modulation process.

Note: Amplitude modulation results in two sidebands. The frequencies above the carrier frequency constitute what is referred to as the "upper sideband"; those below the carrier frequency, constitute the "lower sideband." In conventional AM transmission, both sidebands are present. Transmission in which one sideband is removed is called "single-sideband transmission."

Source: from Federal Standard 1037C and from MIL-STD-188