Arc triangles or systems Arc triangle systems whose idea depends on combining three words in serial syllables (triangles), in which the meaning of the word changes by changing the formation of one letter, starting with opening, then breaking, then joining. Where the letters are arranged but differ in their movements. Triangles are called triangles because they combine all three words in a group, the meanings of which change according to their movements.

It was compiled by Abu Ali Muhammad ibn al-Mustanir, known as Qutub, so it was named after him, and he was the first to write in this field. Al-Asl), arranged them in ascending order, starting with the lightest movements, which is the fatha, and ending with the heaviest, which is the damma.