IPA: //ˌfoʊtəʊˈθɛrəpi//
KK: /ˈfoʊtəʊˌθɛrəpi/
A type of treatment that uses light to help heal certain health problems, especially skin issues.
The doctor recommended phototherapy to treat her skin condition.
Phototherapy → It is formed from "photo-" (from Greek "phōs", meaning light) and "therapy" (from Greek "therapeia", meaning treatment). The word "phototherapy" refers to treatment using light.
Think of 'light' ('photo-') being used for 'treatment' ('therapy') — that's why phototherapy means treatment with light.