How many tones are flat and how many are oblique?

1、One and two tones are flat tones

2、Three and four tones are oblique tones

3、Ping and oblique tones are in terms of Chinese tones, and the traditional four tones are Ping, Shang, Dei, and Jin.

4. Yinping and yangping belong to the flat tones, while Shangsheng, Deosheng, as well as the ancient Chinese entry tones are all categorized as oblique tones.

Flat and oblique tones are the tones of words used in Chinese poetry. The term "flat" refers to straightness, while "oblique" refers to zigzagging. According to rhyme books revised between the Sui and Song dynasties, such as Cheyun and Guangyun, there were four tones in Middle Chinese, known as Ping, Shang, Dei, and Xin. Except for Ping, the other three tones have variations in height, so they are collectively called oblique tones.