原书拼音: /pʰɪŋ²¹ sɪŋ⁵⁵/
level tone (one of the four tones in Middle Chinese)
用例
平聲哀而安,上聲厲而舉,去聲清而遠,入聲直而促。
Level tone is sad and stable. Rising tone is strident and rising. Departing tone is clear and distant. Entering tone is straight and abrupt.
the ngang tone of Vietnamese