Old Korean
As Sino-Korean originates in Old Korean speakers' perception of Middle Chinese phones, elements of Old Korean phonology may be inferred from a comparison of Sino-Korean with Middle Chinese. For instance, Middle Chinese, Middle Korean, and Modern Korean all have a phonemic distinction between the non-aspirated velar stop and its aspirated equivalent, . However, both are regularly reflected in Sino-Korean as . This suggests that was absent in Old Korean.