photodiagnosis

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*dwóh₁
9. Proto-Indo-European*trísinflu.
10. Proto-Indo-European*dwís
11. Ancient Greekδιά (diá)
12. Ancient Greekδια- (dia-)
13. Proto-Indo-European*ǵneh₃-
14. Proto-Indo-European*ǵn̥h₃sḱéti
15. Proto-Hellenic*gignṓskō
16. Ancient Greekγῐγνώσκω (gĭgnṓskō)
17. Ancient Greekδῐαγῐγνώσκω (dĭagĭgnṓskō)
18. Ancient Greekδῐᾰ́γνωσῐς (dĭắgnōsĭs)
19. Latindiagnōsis
20. Englishdiagnosis
21. English todayphotodiagnosis

From photo- + diagnosis.