Capacitively coupled discharge works similarly as DC glow discharge. They both rely on the electric field created by voltage applied on the electrodes to accelerate free-moving electrons to knock out bonded electrons in neutrals. Thus, they are categorized as "E-discharge" in comparison with "H-discharge" (inductively coupled discharge). Unlike DC discharge, there is no fixed cathode or anode in capacitive discharge. An alternating high voltage is applied on both electrodes. Majority of the free-moving electrons will be oscillating back and forth. Compared with DC discharge, they will have less chance of absorption by electrodes and higher chance of ionizing neutral particles. Thus, capacitive discharge offers higher ionization efficiency than DC discharge.