It was a highly synthetic language with a rich declension system as attested by a number of manuscripts from the late 10th and the early 11th centuries.
Few of these changes can still be observed in contemporary written records, thanks to the tendency towards archaicism driven by a desire to preserve the purity of the Cyrilo-Methodian tradition.
The language underwent some morphological changes as well: starting from the time of the Second Bulgarian Empire a confusion of case endings is to be observed along with the increasing use of prepositions in syntax.
This linguistic tendency resulted in the gradual loss of the complex Slavic case system, rendering Bulgarian and Macedonian significantly more analytic than their relatives.
The earliest signs of post-positive definite article dates from the early 13th century with the Dobreyshevo Gospel (Добрейшево Евангелие) where the construction "злыотъ рабъ" ("the evil person") was used.