-Lao (or Laotian) belongs to the Tai language family which also includes Thai, Shan, and languages spoken by smaller, related ethnic groups in Laos, Thailand, Burma, southern China, and northern Vietnam. The languages in the Tai family all share a common grammar and tone structure.

-Lao is spoken not only in Laos but in Northeastern Thailand, an area called “Isan”, and the language itself is often called “Isan” (or pha-sa Ee-san) in Thailand. The languages are basically the same but have some differences between them which developed because of historical differences between the Isan area and Laos.

-The Lao language has many regional varieties in both Laos and Northeastern Thailand. This web site (and the phrasebook on the web site) describe the language as it’s spoken in Vientiane, the capital of the Lao P.D.R. The main difference between these varieties is tonal - different varieties will have some changes in tone from the Vientiane Lao tone chart. There are also some differences in vocabulary from region to region.

-Laos has many ethnic groups. Some of them belong to the Tai family and speak languages related to Lao and Thai but many others speak unrelated languages. The policy in the country is for these ethnic groups to learn to speak and read Lao, and there is a program for Lao as a Second Language in schools with students from non-Lao ethnic groups.

-The Lao P.D.R. hasn't named one variety of Lao as the official language of the country (as in Thailand where Central Thai is the official language), however the Vientiane variety is becoming the unofficial national language. This can be seen in the capital where people from all over the country live. Many people there change their pronunciation or at least recognize that they speak a "regional" variety. The Vientiane variety is spoken on TV and radio and broadcast over the whole country. Newspapers and books are published with vocabulary as used in Vientiane, and if they contain "regional" vocabulary or phrases it's obvious to the reader. Another indication is that people from non-Lao or other Tai ethnic groups who study or work at a high level often try to speak Lao with a Vientiane accent.

-Most of the basic words of Lao have only one syllable. Multi-syllable words are generally higher level and used in religion, academics, and government. They were taken mainly from Sanskrit, the classical language of India, and are often the same as or similar to high-level vocabulary in Thai.

-Lao is a concise language. Prefixes and combinations of basic words are used to make more complex meanings. The sentence structure is also quite simple and "grammar" refers mostly to word order.

-The Lao writing system evolved from Sanskrit. It was first taken by the Khmers during the time of the Angkor Empire then adapted by the Laotians, Northern Thais, and Central Thais into individual though similar alphabets. These alphabets are composed of letters with their own sounds, and are read from left to right like English.

-The Lao alphabet has been reformed several times over the past 50 years. The number of consonant letters was reduced so that words can be read phonetically. This was done so that non-Lao ethnic groups could read the language more easily. The result is that the Lao system doesn't follow Sanskrit as closely as Thai in the spelling of high-level (religious, academic) words, so the Sanskrit origin can't be seen.

-Because Lao words are spelled phonetically there are more homonyms than in Thai. An example is jan in the name of the capital Vientiane (or Viang-jan). The word means "sandalwood" but when it's written in Lao it has the same phonetic spelling as "moon". If you look at the spelling of Vientiane in Thailand, though, it has the extra letters at the end which show that it means "sandalwood" rather than "moon" ("sandalwood" has a thaw tha-han and naw-noo after the phonetic jan while "moon" has a thaw tha-han and a raw reua). You can see the Thai spelling of Vientiane on the signs in Nong Khai leading up to Friendship Bridge. (Laotians also have a story about the origin of the name Vieng-jan which concerns a man named Jan.)

Vocabulary differences (Lao in Laos/Lao in Thailand) - In general, Lao in the Lao P.D.R. has been influenced by French while Lao in Northeastern Thailand has been influenced by Thai and English. Some major differences are as follows:

-Words borrowed from European languages have the French pronunciation in Laos but the English pronunciation in Thailand. An example is “wine” which is waeng in Laos and wai in Thailand. (Note that nasalized French endings become "ng" in Laos.)

-Lao speakers in Thailand use Thai words for some common nouns rather than the Lao word. Examples are “paper” (jia in Laos, gra-dat in Thailand), “book” (peum in Laos, nang-seu in Thailand), and “bread” (kao-jee in Laos and ka-nom pang in Thailand). Lao speakers in Thailand may also use the Thai phrases for “hello” and “thank you”.

-Words in Laos taken from Vietnamese and not used in Thailand are feuh for “noodle soup” (called guay-tio in Thailand) and viak for “work”. (“To work” is hayt-viak in Laos and hayt-ngan in Lao-speaking Thailand.)

-Official words such as “province” and “district” follow the Thai designation in Thailand. The systems for telling time are also different in the two countries.

-Two common words are pronounced differently: the Mekong River is called Mae-nam Kawng in Laos and Mae-nam Kong in Thailand, and the word for the Laotian string-tying ceremony is ba-see in Laos and bai-see in Thailand.