Explanation of the initial sounds初聲解
正音初聲，卽韻書之字母也。聲音由此而生，故曰母。如牙音君字初聲是ㄱ，ㄱ與ᅟᅮᆫ而爲군。快字初聲是ㅋ，ㅋ與ㅙ而爲쾌〯。虯字初聲是ㄲ，ㄲ與ㅠ而爲뀨。業字初聲是ㆁ，ㆁ與ᅟᅥᆸ而爲ᅌᅥᆸ之類。舌之斗呑覃那，脣之彆漂步彌，齒之卽侵慈戌邪，喉之挹虛洪欲，半舌半齒之閭穰，皆倣此。訣曰
The initials of the Correct Sounds are just the letter-mothers of the rhyme books. Since sound comes forth from them, they are called mothers.
The initial of the molar character 君 gun is ㄱ; ㄱ joins with ᅟᅮᆫ to make 군. The initial of 快 kwae is ㅋ; ㅋ joins with ㅙ to make 쾌〯. The initial of 虯 gyu is ㄲ; ㄲ joins with ㅠ to make 뀨. The initial of 業 eop is ㆁ; ㆁ joins with ᅟᅥᆸ to make ᅌᅥᆸ. And so on in like manner.
The lingual 斗 du, 呑 tan, 覃 dam and 那 na; the labial 彆 byeol, 漂 pyo, 步 bo and 彌 mi; the dental 卽 jeuk, 侵 chim, 慈 ja, 戌 sul and 邪 sa; the guttural 挹 eup, 虛 heo, 洪 hong and 欲 yok; and the semi-lingual and semi-dental 閭 ryeo and 穰 yang — all of these follow this same pattern. Let us sing it in brief.
君快虯業其聲牙 舌聲斗呑及覃那 彆漂步彌則是脣 齒有卽侵慈戌邪 挹虛洪欲迺喉聲 閭爲半舌穰半齒 二十三字是爲母 萬聲生生皆自此
gun, kwae, gyu and eop — their sounds are of the molars; in the lingual sounds there are du and tan, and dam and na. byeol, pyo, bo and mi are of the lips indeed, and in the teeth there are jeuk, chim, ja, sul and sa. eup, heo, hong and yok are the guttural sounds, and ryeo becomes the semi-tongue and yang the semi-teeth. Twenty-three letters are these mothers, and all the sounds there are come forth and are born from here.