photodynamics

The story

1. Proto-Indo-European*bʰeh₂-
2. Proto-Indo-European*bʰéh₂os
3. Proto-Hellenic*pʰáwos
4. Ancient Greekφᾰ́ος (phắos)
5. Ancient Greekφῶς (phôs)
6. Ancient Greekφωτο- (phōto-)
7. Englishphoto-
8. Proto-Indo-European*dewh₂-
9. Proto-Hellenic*dunamai
10. Ancient Greekδῠ́νᾰμαι (dŭ́nămai)
11. Ancient Greekδύναμις (dúnamis)
12. Ancient Greekδυναμικός (dunamikós)
13. Frenchdynamique
14. Englishdynamic
15. Englishdynamics
16. English todayphotodynamics

From photo- + dynamics.