Thai,[a] Central Thai[b] (historically Siamese;[c] Thai: ภาษาไทย), is the national language of Thailand and de facto official language; it is the first language of the Central Thai people[d] and most Thai Chinese, depending on age. It is a member of the Tai group of the Kra–Dai language family, and one of over 60 languages of Thailand. Over half of Thai vocabulary is derived from or borrowed from Pali, Sanskrit, Mon and Old Khmer. It is a tonal and analytic language, similar to Chinese and Vietnamese.
Thai has a complex orthography and system of relational markers. Spoken Thai is partly, depending on standard sociolinguistic factors such as age, gender, class, spatial proximity, and the urban/rural divide, mutually intelligible with Lao, Isan, and some fellow Southwestern Tai languages. These languages are written with slightly different scripts but are linguistically similar and effectively form a dialect continuum.