The story
- Proto-Indo-European*bʰeh₂-
- Proto-Indo-European*bʰéh₂os
- Proto-Hellenic*pʰáwos
- Ancient Greekφᾰ́ος (phắos)
- Ancient Greekφῶς (phôs)
- Ancient Greekφωτο- (phōto-)
- Englishphoto-
- Proto-Indo-European*h₁ey-
- Proto-Indo-European*h₁éyti
- Proto-Hellenic*éimi
- Ancient Greekἰόν (ión)
- Englishion
- Englishionise
- Englishionisation
- English todayphotoionisation
From photo- + ionisation.
Etymology from Wiktionary, CC BY-SA 4.0.