Details:

1, a phonological term. The representative word of initials, abbreviated as "mother".

Wang Songying-lin's Yuhai Wen Yi Primary School: "Guang (Sima Guang) has a rhyme, with 384 sounds in 36 words." In the Qing Dynasty, Qian Daxin wrote "A New Record of Letters of Fasting by Ten Drivers": "Thirty-six letters were unknown before the Tang Dynasty. According to legend, it is because monks keep warm, and keeping warm is also a shaman in the late Tang Dynasty.

2. The minimum writing unit of pinyin characters or phonetic symbols. Such as: English letters; Chinese Pinyin.