IPA: /ˌɛlɛkˈtroʊˌθɛrəpi/
KK: /ɪˌlɛk.trəʊˈθɛr.ə.pi/
A type of medical treatment that uses electric currents to help heal or relieve pain.
The doctor recommended electrotherapy to help with my muscle pain.
Electrotherapy is formed from "electro-" (from Greek "ēlektron", meaning amber or electricity) and "therapy" (from Greek "therapeia", meaning treatment or healing). The word refers to the treatment of disease by the use of electricity.
Think of 'electricity' ('electro-') being used for 'treatment' ('therapy') — that's how electrotherapy helps in healing.