Electronic warfare (EW) is the collective term for any operation by army, police or other governmental or non-governmental forces in which the electromagnetic spectrum or directed energy is used to support and protect against hostile activities. Widely in use at military actions since beginning of 20th century, EW became one of the most important components of modern military and non-military operations.

EW can be applied from air, sea, land and space by manned and unmanned systems and can target communication, radar or other services.

Activities used in EW include: electrooptical-infrared and radio frequency countermeasures; EM (electromagnetic) compatibility and deception, interference, intrusion and jamming, electronic masking, probing, reconnaissance, and intelligence, electronics security, EW reprogramming, emission control and spectrum management.

EW includes three mains subdivisions:

Electronic Attack (EA): 
EM Jamming
EM Deception
Directed energy

Electronic Protection (EP): 
Threat warning
Direction finding

Electronic Warfare Support (ES): 
Spectrum management
Acquisition and measurement of the frequency spectrum
Emission control