bidialectal

The story

1. Proto-Indo-European*dwóh₁
2. Proto-Indo-European*dwi-
3. Proto-Italic*dwi-
4. Latinbi-
5. Englishbi-
6. Proto-Indo-European*dwóh₁
7. Proto-Indo-European*trísinflu.
8. Proto-Indo-European*dwís
9. Ancient Greekδιά (diá)
10. Ancient Greekδῐᾰ- (dĭă-)
11. Proto-Indo-European*leǵ-
12. Proto-Indo-European*léǵ-e-ti
13. Proto-Hellenic*légō
14. Ancient Greekλέγω (légō)
15. Ancient Greekδιαλέγομαι (dialégomai)
16. Ancient Greekδῐᾰ́λεκτος (dĭắlektos)
17. Latindialecto
18. Middle Frenchdialecte
19. Englishdialect
20. Proto-Indo-European*h₂el-
21. Proto-Indo-European*h₂élisder.?
22. Englishdialectal
23. English todaybidialectal

From bi- + dialectal.