Electronic devices operate in a world of electromagnetic (EM) fields of various strengths. Each device is not only subject to interference from those EM fields, but may itself be a source of EM interference to other devices. EM interference can be conducted or radiated, either degrading or disrupting the performance of an electronic device.
Lower-frequency EM interference, such as from power lines, is usually referred to as electromagnetic interference (EMI). Higher-frequency EM interference, such as from radio waves, is known as radio frequency interference (RFI), although the two terms are often used interchangeably. Electromagnetic compatibility (EMC) refers to the fact that an electronic device has been found to operate effectively in this world of EM fields, not causing interference and not affected by the interference around it.