Thai, or more precisely Siamese or Central Thai, is the national and official language of Thailand and the native language of the Thai people and Thai Chinese. Thai is a member of the Tai group of the Tai–Kadai language family. Over half of the words in Thai are borrowed from Pali, Sanskrit and Old Khmer. It is a tonal and analytic language. Thai also has a complex orthography and relational markers. Thai is mutually intelligible with Lao. Script Many scholars believe that the Thai script is derived from the Khmer script, which is modeled after the Brahmic script from the Indic family. However, in appearance, Thai is closer to Thai Dam script, which may have the same Indian origins as the Khmer script. The language and its script are closely related to the Lao language and script. Most literate Lao are able to read and understand Thai, as more than half of the Thai vocabulary, grammar, intonation, vowels and so forth are common with the Lao language. Much like the Burmese adopted the Mon script (which also has Indic origins), the Thais adopted and modified the Khmer script to create their own writing system. History Thai has undergone various historical sound changes. Some of the most significant changes, at least in terms of consonants and tones, occurred between Old Thai spoken when the language was first written and Thai of present, reflected in the orthography. Transliteration The ISO published an international standard for the transliteration of Thai into Roman script in September 2003 (ISO 11940). By adding diacritics to the Latin letters, it makes the transcription reversible, making it a true transliteration. Notably, this system is used by Google Translate, although it seems not to appear in many other contexts, such as textbooks and other instructional media. This may be because the particular problems of writing Thai for foreigners, including silent letters and placement of vowel markers, decrease the usefulness of literal transliteration.