Dobro and Its Cyrillic Counterpart

Cyrillic dobro is the same letter by name, sound and position, and it is numbered four where Glagolitic numbers five. The two alphabets are now running one apart, and they will stay at least that far apart for the rest of the order.

The pair is a good place to see what the two scripts actually share. The name is the same Slavonic word in both. The sound is the same. The place in the sequence is the same, fifth in a list that both traditions recite in the same order and teach with the same mnemonic sentence. What is not shared is the shape, and no argument about the relationship between the scripts has ever turned on shape alone for this letter, because the Cyrillic form is plainly a Greek delta adapted and the Glagolitic form is plainly not a Greek delta.

That asymmetry is the shape of the whole problem. Cyrillic can be accounted for letter by letter: Greek uncial where Greek has the sound, and something else where it does not. Glagolitic cannot, and the something else in Cyrillic is often taken to be Glagolitic itself, which would make the newer script a witness to the older one. The direction of that borrowing is argued rather than demonstrated, and the earliest manuscripts of either script are a century or more younger than the alphabet they use.