What is the relationship between the two Latin words educo? Specifically, why the short vowel in [e:duka:-] "educate"? Is it a zero grade? I would have thought the [-a:-] formative was comparatively late, after the grade ablaut stage - but I'm very much an amateur here. Also, I'd have thought the specialization of meaning would go like this: the transparent 3rd conjugation compound [e:-du:k-] would begin life as "lead out" then become specialized to "educate", after which a new verb would be needed to mean "lead out". The productive suffix is [-a:-], so I'd expect 1st conjugation [e:du:ka:-] (preserving the long root vowel) to be created for this. But that's not how it happened. Any ideas on this? Skeat just mentions the two are connected, and Sihler doesn't seem to cover it.