Old Burmese was an early form of the Burmese language, as attested in the stone inscriptions of Pagan, and is the oldest phase of Burmese linguistic history. The transition to Middle Burmese occurred in the 1500s. The transition to Middle Burmese included phonological changes (e.g. mergers of sound pairs that were distinct in Old Burmese) as well as accompanying changes in the underlying orthography.