photoresponse

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-Italic *wre-
Latin re-
Proto-Indo-European *spend-
Proto-Indo-European *spondéyeti
Proto-Italic *spondejō
Proto-Italic *spondeō
Latin spondeō
Latin respondeō
Latin respōnsumbor.
Old French respunsbor.
Middle English respounse
English response
English photoresponse
From photo- + response.