phototherapy

Etymology tree
Proto-Indo-European *bʰeh₂-
Proto-Indo-European *bʰéh₂os
Proto-Hellenic *pʰáwos
Ancient Greek φᾰ́ος (phắos)
Ancient Greek φῶς (phôs)
Ancient Greek φωτο- (phōto-)der.
English photo-
Proto-Indo-European *treb-der.?
Ancient Greek θερᾰ́πων (therắpōn)
Ancient Greek -εύς (-eús)
Ancient Greek -εύω (-eúō)
Ancient Greek θεραπεύω (therapeúō)
Proto-Indo-European *-h₂
Proto-Indo-European *-éh₂
Proto-Indo-European *-i-eh₂
Proto-Hellenic *-íā
Ancient Greek -ία (-ía)
Ancient Greek θεραπεία (therapeía)bor.
New Latin therapīabor.
English therapy
English phototherapy
From photo- + therapy.