For example, the Arabic language lacks a voiceless bilabial plosive (the [p] sound), so many languages add their own letter to represent [p] in the script, though the specific letter used varies from language to language. These modifications tend to fall into groups: all the Indian and Turkic languages written in the Arabic script tend to use the Persian modified letters, whereas the languages of Indonesia tend to imitate those of Jawi. The modified version of the Arabic script originally devised for use with Persian is known as the Perso-Arabic script by scholars.