Final Consonants and Tones
Middle Chinese syllables could end with glides /j/ or /w/, nasals /m/, /n/ or /ŋ/, or stops /p/, /t/ or /k/. Syllables with vocalic or nasal endings could occur with one of three tonal contours, called level (píng 平), rising (shǎng 上) or departing (qù 去). Syllables with final stops were traditionally treated as a fourth tone category, the entering tone (rù 入), because the stops were distributed in the same way as the corresponding final nasals.
While northern and central varieties have lost some of the Middle Chinese final consonants, they are retained by most southern Chinese varieties, though sometimes affected by sound shifts. They are most faithfully preserved in Yue dialects. Final stops have disappeared entirely in most Mandarin dialects, including the Beijing-based standard, with the syllables distributed across the other tones. For example, the characters 裔, 屹, 藝, 憶, 譯, 懿, 肄, 翳, 邑, and 佚 are all pronounced yì in Mandarin, but they are all different in Yue (Cantonese jeoi6, ngat6, ngai6, jik1, jik6, ji3, ji6, ai3, jap1, and jat6, respectively).
Similarly, in Mandarin dialects the Middle Chinese final /m/ has merged with /n/, but the distinction is maintained in southern dialects such as Hakka, Min and Yue. For example, Cantonese has taahm (譚) and tàahn (壇) versus Mandarin tán, yìhm (鹽) and yìhn (言) versus Mandarin yán, tìm (添) and tìn (天) versus Mandarin tiān, and hàhm (含) and hòhn (寒) versus Mandarin hán.
Middle Chinese is described in contemporary dictionaries as having four tones, where the fourth category, the entering tone, consists of syllables with final stops. Many modern Chinese varieties contain traces of a split of each of these four tones into two registers, an upper or yīn register from voiceless initials and a lower or yáng register from voiced initials. Mandarin dialects retain the register distinction only in the level tone, yielding the first and second tones of the standard language (corresponding to the first and fourth tones in Cantonese), but have merged several of the other categories. Most Yue dialects have retained all eight categories, with a further split of the upper entering tone conditioned by vowel length, as also found in neighbouring Tai dialects. A few dialects spoken in Guangxi, such as the Bobai dialect, have also split the lower entering tone.