喉音和牙音（今名舌根音）由于发音部位靠近，常常互谐互通。这是喉牙音中最常见、最重要并贯通古今的语音现象，是汉语声母系统中一个非常有用的、饶有趣味的音韵学原理。本文通过２１组古今字、通假字、异体字、繁简字来论证这一重要的语音规律 Guttural sounds and dental sounds (now called the tongue root tone) due to the pronunciation of the parts close, often interoperable with each other. This is the most common, the most important and ancient phonetic phenomenon in the throat sounds. It is a very useful and interesting phonetics principle in the Chinese initial consonant system. This article proves this important phonetic law through 21 groups of ancient and modern Chinese characters, Tongshi characters, different characters and traditional Chinese characters