Lao, which is also widely known in English as Laotian and Laothian, is the official language of Laos. Lao is a tonal language and is a close relative of the languages of Thailand's north-eastern Isan region. Standard Lao is so close to Thai that native speakers of the two languages can readily understand one another. The Lao language can be seperated into five major dialectical groups: Southern Lao (Champasak), Central Lao (Khammouan), North-Eastern Lao (Xieng Khouang), Vientiane Lao, and Northern Lao (Luang Prabang). The Lao alphabet is derived from the same simple alphabet used in the Thai script which, itself, was modified from a southern Indian script with Khmer origins. The Lao writing system is made up of 33 consonants and 28 vowels representing 21 and 27 original sounds, respectively. Lao is written from left to right.