Electrostatic discharge (ESD) is the sudden flow of electricity between two objects caused by contact, an electrical short or dielectric breakdown. 

ESD can be caused by a buildup of static electricity by tribocharging, or by electrostatic induction. 

ESD includes spectacular electric sparks, but also less dramatic forms which may be neither seen nor heard, yet still are large enough to cause damage to sensitive electronic devices. Electric sparks require a field strength above about 4 kV/cm in air, as notably occurs in lightning strikes. 

Other forms of ESD include corona discharge from sharp electrodes and brush discharge from blunt electrodes.