The paper explores the grammatical transformations in the paradigm of nouns from the cycle Za Serafimite (On the Seraphim) by St. John Chrysostom. The transformations detected have been compared to manuscripts from the 12th – 14th centuries: the Yagichev Zlatoust, Tarnovo recension of the Verse Prolog, the Synaxaria for the Triodion by Zacchaeus the Philosopher, the Life of St. Antony, the Chronicle of Manasses, Boril’s Synodikon, the Song of Songs from the Rila Monastery, Patriarch Photios’s Letter to Knyaz Boris, Philotheus Kokkinos’s translation of the Panegyric to All Saints. The paper also shows the chronology and frequency of the changes that took place. It explores the grammatical relations and the continuity between a pre-Euthymian translation and the Tarnovo Literary School, and makes a synchronic inquiry into a word class, which indicates the historical development of the standard Bulgarian language and the tendency towards analyticism.