Geographic distribution
As the national language of the majority ethnic group, Vietnamese is spoken throughout Vietnam by the Vietnamese people, as well as by ethnic minorities. It is also spoken in overseas Vietnamese communities, most notably in the United States, where it has more than one million speakers and is the seventh most-spoken language (it is 3rd in Texas, 4th in Arkansas and Louisiana, and 5th in California). In Australia, it is the sixth most-spoken language.
According to the Ethnologue, Vietnamese is also spoken by substantial numbers of people in Australia, Cambodia, Canada, China, Côte d’Ivoire, Czech Republic, Finland, France, Germany, Laos, Martinique, the Netherlands, New Caledonia, Norway, the Philippines, the Russian Federation, Senegal, Taiwan, Thailand, the United Kingdom, the United States, and Vanuatu.

Genealogical classification
Vietnamese was identified more than 150 years ago to be part of the Mon-Khmer branch of the Austroasiatic language family (a family that also includes Khmer, spoken in Cambodia, as well as various tribal and regional languages, such as the Munda and Khasi languages spoken in eastern India, and others in southern China). Later, M??ng was found to be more closely related to Vietnamese than other Mon-Khmer languages, and a Vi?t-M??ng sub-grouping was established. As data on more Mon-Khmer languages were acquired, other minority languages (such as Thav?ng, Ch?t languages, Hung, etc.) were found to share Vi?t-M??ng characteristics, and the Vi?t-M??ng term was renamed to Vietic. The older term Vi?t-M??ng now refers to a lower sub-grouping (within an eastern Vietic branch) consisting of Vietnamese dialects, M??ng dialects, and Ngu?n (of Qu?ng Bình Province).

Language policy
While spoken by the Vietnamese people for millennia, written Vietnamese did not become the official administrative language of Vietnam until the 20th century. For most of its history, the entity now known as Vietnam used written classical Chinese, whereas written Vietnamese in the form of Ch? nôm was invented in the 13th century and extensively used in the 17-18 centuries for poetry and literature. Ch? nôm was used for administrative purposes during the brief H? and Tây S?n Dynasties. During French colonialism, French superseded Chinese in administration. It was not until independence from France that Vietnamese was used officially. It is the language of instruction in schools and universities and is the language for official business.

History
It seems likely that in the distant past, Vietnamese shared more characteristics common to other languages in the Austroasiatic family, such as an inflectional morphology and a richer set of consonant clusters, which have subsequently disappeared from the language. However, Vietnamese appears to have been heavily influenced by its location in the Southeast Asian sprachbund, with the result that it has acquired or converged toward characteristics such as isolating morphology and tonogenesis. These characteristics, which may or may not have been part of Proto-Austro-Asiatic, nonetheless have become part of many of the phylogenetically unrelated languages of Southeast Asia; for example, Thai (one of the Kradai languages), Tsat (a member of the Malayo-Polynesian group within Austronesian), and Vietnamese each developed tones as a phonemic feature, although their respective ancestral languages were not originally tonal.[citation needed] At present, Vietnamese has similarities with both Chinese and French due to the influence of the French presence.
The ancestor of the Vietnamese language was originally based in the area of the Red River in what is now northern Vietnam, and during the subsequent expansion of the Vietnamese language and people into what is now central and southern Vietnam (through conquest of the ancient nation of Champa and the Khmer people of the Mekong Delta in the vicinity of present-day Ho Chi Minh City (Saigon), characteristic tonal variations have emerged.

Vietnamese was linguistically influenced primarily by Chinese, which came to predominate politically in the 2nd century B.C. With the rise of Chinese political dominance came radical importation of Chinese vocabulary and grammatical influence. As Chinese was, for a prolonged period, the only medium of literature and government, as well as the primary written language of the ruling class in Vietnam, much of the Vietnamese lexicon in all realms consists of Hán Vi?t (Sino-Vietnamese) words. In fact, as the vernacular language of Vietnam gradually grew in prestige toward the beginning of the second millennium, the Vietnamese language was written using Chinese characters (using both the original Chinese characters, called Hán t?, as well as a system of newly created and modified characters called Ch? nôm) adapted to write Vietnamese, in a similar pattern as used in Japan (kanji), Korea (hanja), and other countries in the Sinosphere. The Nôm writing reached its zenith in the 18th century when many Vietnamese writers and poets composed their works in Ch? Nôm, most notably Nguy?n Du and H? Xuân H??ng (dubbed “the Queen of Nôm poetry”).

As contact with the West grew, the Qu?c Ng? system of Romanized writing was developed in the 17th century by Portuguese and other Europeans involved in proselytizing and trade in Vietnam. When France invaded Vietnam in the late 19th century, French gradually replaced Chinese as the official language in education and government. Vietnamese adopted many French terms, such as ??m (dame, from madame), ga (train station, from gare), s? mi (shirt, from chemise), and búp bê (doll, from poupée). In addition, many Sino-Vietnamese terms were devised for Western ideas imported through the French. However, the Romanized script did not come to predominate until the beginning of the 20th century, when education became widespread and a simpler writing system was found more expedient for teaching and communication with the general population.

Vocabulary
As a result of a thousand years of Chinese occupation, much of the Vietnamese lexicon relating to science and politics is derived from Chinese. At least 60% of the vocabulary has Chinese roots, not including naturalized word borrowings from China, although many compound words are Sino-Vietnamese, composed of native Vietnamese words combined with Chinese borrowings. One can usually distinguish between a native Vietnamese word and a Chinese borrowing if it can be reduplicated or its meaning does not change when the tone is shifted. As a result of French colonization, Vietnamese also has words borrowed from the French language, for example cà phê (from French café). Nowadays, many new words are being added to the language’s lexicon; these are usually borrowed from English, for example TV (though usually seen in the written form as tivi). Sometimes these borrowings are calques literally translated into Vietnamese for example, ‘software’ is calqued into ph?n m?m, which literally means “soft part”.

Phonology
Vowels
Like other southeast Asian languages, Vietnamese has a comparatively large number of vowels. Below is a vowel diagram of Hanoi Vietnamese.

Front, central, and low vowels (i, ê, e, ?, â, ?, ?, a) are unrounded, whereas the back vowels (u, ô, o) are rounded. The vowels â [?] and ? [a] are pronounced very short, much shorter than the other vowels. Thus, ? and â are basically pronounced the same except that ? [??] is long while â [?] is short — the same applies to the low vowels long a [a?] and short ? [a].
In addition to single vowels (or monophthongs), Vietnamese has diphthongs and triphthongs. The diphthongs consist of a main vowel component followed by a shorter semivowel offglide to a high front position [?], a high back position [?], or a central position [?].

The centering diphthongs are formed with only the three high vowels (i, ?, u) as the main vowel. They are generally spelled as ia, ?a, ua when they end a word and are spelled iê, ??, uô, respectively, when they are followed by a consonant. There are also restrictions on the high offglides: the high front offglide cannot occur after a front vowel (i, ê, e) nucleus and the high back offglide cannot occur after a back vowel (u, ô, o) nucleus[10].
The correspondence between the orthography and pronunciation is complicated. For example, the offglide [??] is usually written as i however, it may also be represented with y. In addition, in the diphthongs [a??] and [a???] the letters y and i also indicate the pronunciation of the main vowel: ay = ? + [??], ai = a + [??]. Thus, tay “hand” is [ta??] while tai “ear” is [ta???]. Similarly, u and o indicate different pronunciations of the main vowel: au = ? + [??], ao = a + [??]. Thus, thau “brass” is [t?a??] while thao “raw silk” is [t?a???].
The four triphthongs are formed by adding front and back offglides to the centering diphthongs. Similarly to the restrictions involving diphthongs, a triphthong with front nucleus cannot have a front offglide (after the centering glide) and a triphthong with a back nucleus cannot have a back offglide.
With regards to the front and back offglides [??, ??], many phonological descriptions analyze these as consonant glides /j, w/. Thus, a word such as ?âu “where”, phonetically [????], would be phonemicized as /??w/.

Tones

Pitch contours and duration of the six Northern Vietnamese tones as uttered by a male speaker (not from Hanoi). Fundamental frequency is plotted over time. From Nguy?n & Edmondson (1998).

Vietnamese vowels are all pronounced with an inherent tone. Tones differ in:

Tone is indicated by diacritics written above or below the vowel (most of the tone diacritics appear above the vowel; however, the n?ng tone dot diacritic goes below the vowel).[12] The six tones in the northern varieties (including Hanoi) are:

Other dialects of Vietnamese have fewer tones (typically only five). See the language variation section for a brief survey of tonal differences among dialects.
In Vietnamese poetry, tones are classed into two groups:

Tone group
Tones within tone group
b?ng “level, flat”
ngang and huy?n
tr?c “oblique, sharp”
s?c, h?i, ngã, and n?ng
Words with tones belonging to particular tone group must occur in certain positions with the poetic verse.

Consonants
The consonants that occur in Vietnamese are listed below in the Vietnamese orthography with the phonetic pronunciation to the right.
 

Some consonant sounds are written with only one letter (like “p”), other consonant sounds are written with a two-letter digraph (like “ph”), and others are written with more than one letter or digraph (the velar stop is written variously as “c”, “k”, or “q”).
Not all dialects of Vietnamese have the same consonant in a given word (although all dialects use the same spelling in the written language). See the language variation section for further elaboration.
The analysis of syllable-final orthographic ch and nh in Hanoi Vietnamese has had different analyses. One analysis has final ch, nh as being phonemes /c, ?/ contrasting with syllable-final t, c /t, k/ and n, ng /n, ?/ and identifies final ch with the syllable-initial ch /c/. The other analysis has final ch and nh as predictable allophonic variants of the velar phonemes /k/ and /?/ that occur before upper front vowels i /i/ and ê /e/. (See Vietnamese phonology: Analysis of final ch, nh for further details.)

Language variation
There are various mutually intelligible regional varieties (or dialects), the main four being:

Vietnamese has traditionally been divided into three dialect regions: North, Central, and South. However, Michel Fergus and Nguy?n Tài C?n offer evidence for considering a North-Central region separate from Central. The term Haut-Annam refers to dialects spoken from northern Ngh? An Province to southern (former) Th?a Thiên Province that preserve archaic features (like consonant clusters and undiphthongized vowels) that have been lost in other modern dialects.

These dialect regions differ mostly in their sound systems (see below), but also in vocabulary (including basic vocabulary, non-basic vocabulary, and grammatical words) and grammar.[14] The North-central and Central regional varieties, which have a significant amount of vocabulary differences, are generally less mutually intelligible to Northern and Southern speakers. There is less internal variation within the Southern region than the other regions due to its relatively late settlement by Vietnamese speakers (in around the end of the 15th century). The North-central region is particularly conservative. Along the coastal areas, regional variation has been neutralized to a certain extent, while more mountainous regions preserve more variation. As for sociolinguistic attitudes, the North-central varieties are often felt to be “peculiar” or “difficult to understand” by speakers of other dialects.

It should be noted that the large movements of people between North and South beginning in the mid-20th century and continuing to this day have resulted in a significant number of Southern residents speaking in the Northern accent/dialect and, to a lesser extent, Northern residents speaking in the Southern accent/dialect. Following the Geneva Accords of 1954 that called for the “temporary” division of the country, almost a million Northern speakers (mainly from Hanoi and the surrounding Red River Delta areas) moved South (mainly to Saigon, now Ho Chi Minh City, and the surrounding areas.) About a third of that number of people made the move in the reverse direction.

Following the reunification of Vietnam in 1975-76, Northern and North-Central speakers from the densely populated Red River Delta and the traditionally poorer provinces of Nghe An, Ha Tinh and Quang Binh have continued to move South to look for better economic opportunities. Additionally, government and military personnel are posted to various locations throughout the country, often away from their home regions. More recently, the growth of the free market system has resulted in business people and tourists traveling to distant parts of Vietnam. These movements have resulted in some small blending of the dialects but, more significantly, have made the Northern dialect more easily understood in the South and vice versa. It is also interesting to note that most Southerners, when singing modern/popular Vietnamese songs, would do so in the Northern accent. This is true in Vietnam as well as in the overseas Vietnamese communities.

Regional variation in grammatical words

The syllable-initial ch and tr digraphs are pronounced distinctly in North-central, Central, and Southern varieties, but are merged in Northern varieties (i.e. they are both pronounced the same way). The North-central varieties preserve three distinct pronunciations for d, gi, and r whereas the North has a three-way merger and the Central and South have a merger of d and gi while keeping r distinct. At the end of syllables, palatals ch and nh have merged with alveolars t and n, which, in turn, have also partially merged with velars c and ng in Central and Southern varieties.

Regional consonant correspondences

In addition to the regional variation described above, there is also a merger of l and n in certain rural varieties:

l, n variation

Variation between l and n can be found even in mainstream Vietnamese in certain words. For example, the numeral “five” appears as n?m by itself and in compound numerals like n?m m??i “fifty” but appears as l?m in m??i l?m “fifteen”. (See Vietnamese syntax: Cardinal numerals.) In some northern varieties, this numeral appears with an initial nh instead of l: hai m??i nh?m “twenty-five” vs. mainstream hai m??i l?m.
The consonant clusters that were originally present in Middle Vietnamese (of the 17th century) have been lost in almost all modern Vietnamese varieties (but retained in other closely related Vietic languages). However, some speech communities have preserved some of these archaic clusters: “sky” is bl?i with a cluster in H?o Nho (Yên Mô prefecture, Ninh Binh Province) but tr?i in Southern Vietnamese and gi?i in Hanoi Vietnamese (initial single consonants /??, z/, respectively).

Tones
Generally, the Northern varieties have six tones while those in other regions have five tones. The h?i and ngã tones are distinct in North and some North-central varieties (although often with different pitch contours) but have merged in Central, Southern, and some North-central varieties (also with different pitch contours). Some North-central varieties (such as Hà T?nh Vietnamese) have a merger of the ngã and n?ng tones while keeping the h?i tone distinct. Still other North-central varieties have a three-way merger of h?i, ngã, and n?ng resulting in a four-tone system. In addition, there are several phonetic differences (mostly in pitch contour and phonation type) in the tones among dialects.

Regional tone correspondences

The table above shows the pitch contour of each tone using Chao tone number notation (where 1 = lowest pitch, 5 = highest pitch); glottalization (creaky, stiff, harsh) is indicated with the symbol; breathy voice with ; glottal stop with ; sub-dialectal variants are separated with commas. (See also the tone section below.)

Grammar
Vietnamese, like many languages in Southeast Asia, is an analytic (or isolating) language. Vietnamese does not use morphological marking of case, gender, number or tense (and, as a result, has no finite/nonfinite distinction).[18] Also like other languages in the region, Vietnamese syntax conforms to Subject Verb Object word order, is head-initial (displaying modified-modifier ordering), and has a noun classifier system. Additionally, it is pro-drop, wh-in-situ, and allows verb serialization.
Some Vietnamese sentences with English word glosses and translations are provided below.

Writing system
Main article: Vietnamese alphabet
Currently, the written language uses the Vietnamese alphabet (qu?c ng? or “national script”, literally “national language”), based on the Latin alphabet. Originally a Romanization of Vietnamese, it was codified in the 17th century by a French Jesuit missionary named Alexandre de Rhodes (1591–1660), based on works of earlier Portuguese missionaries (Gaspar do Amaral and António Barbosa). The use of the script was gradually extended from its initial domain in Christian writing to become more popular among the general public.

Under French colonial rule, the script became official and required for all public documents in 1910 by issue of a decree by the French Résident Supérieur of the protectorate of Tonkin. By the end of first half 20th century virtually all writings were done in qu?c ng?.
Changes in the script were made by French scholars and administrators and by conferences held after independence during 1954–1974. The script now reflects a so-called Middle Vietnamese dialect that has vowels and final consonants most similar to northern dialects and initial consonants most similar to southern dialects (Nguy?n 1996). This Middle Vietnamese is presumably close to the Hanoi variety as spoken sometime after 1600 but before the present. (This is not unlike how English orthography is based on the Chancery Standard of late Middle English, with many spellings retained even after significant phonetic change.)

Before French rule, the first two Vietnamese writing systems were based on Chinese script:

• the standard Chinese character set called ch? nho (scholar’s characters,