ontological

The story

1. Proto-Indo-European*h₁es-
2. Proto-Indo-European*h₁sónts
3. Proto-Hellenic*ehonts
4. Ancient Greekὤν, ὄντος (ṓn, óntos)
5. Proto-Indo-European*leǵ-
6. Proto-Indo-European*lóǵos
7. Proto-Hellenic*lógos
8. Ancient Greekλόγος (lógos)
9. New Latinontologia
10. Englishontology
11. Proto-Indo-European*h₂el-
12. Proto-Indo-European*h₂élisder.?
13. English todayontological

From ontology + -ical.