AbstractThis study is based on a number of starting points from the theory of sounds according to Khalil bin Ahmed Al-Farahidi. The source of the sound is from the outside air moving in the form of waves until it reaches the human ear, so hearing is the natural sense of understanding the sound. And people was able to perceive the phoneme that we call speech. According to Arabic scholars, Khalil was the first to author an Arabic dictionary called "Kitab al-Ain", which studies the sounds of language as a unit of phoneme and word units described in the introduction to his book. The purpose of this research is to know his thinking about sounds. This research is of the type of a desk study by collecting data from books and other sources related to the research. In analyzing her research, the researcher used the analytical and descriptive method to examine scientific research from facts with a descriptive and structured approach. The steps for conducting this research are data collection, classifica.....