Sino-Vietnamese vocabulary (Vietnamese: từ Hán Việt, Chữ Hán: 詞漢越, literally 'Chinese-Vietnamese words') is a layer of about 3,000 monosyllabic morphemes of the Vietnamese language borrowed from Literary Chinese with consistent pronunciations based on Middle Chinese. Compounds using these morphemes are used extensively in cultural and technical vocabulary. Together with Sino-Korean and Sino-Japanese vocabularies, Sino-Vietnamese has been used in the reconstruction of the sound categories of Middle Chinese. Samuel Martin grouped the three together as "Sino-xenic". There is also an Old Sino-Vietnamese layer consisting of a few hundred words borrowed individually from Chinese in earlier periods. These words are treated by speakers as native words. More recent loans from southern varieties of Chinese, usually names of foodstuffs such as lạp xưởng 'Chinese sausage' (from Cantonese), are not treated as Sino-Vietnamese but more direct borrowings.^[1]

Estimates of the proportion of words of Chinese origin in the Vietnamese lexicon vary from one third to half and even to 70%.^[2][3][4] The proportion tends towards the lower end in speech and towards the higher end in technical writing.^[5] In the famous Từ điển tiếng Việt [vi] dictionary by Vietnamese linguist Hoàng Phê [vi], about 40% percent of vocabulary are of Chinese origin.^[6]

It has also been theorised that Sino-Vietnamese words came from a language shift from a population of Annamese Middle Chinese speakers that lived in Red River Delta in northern Vietnam to proto-Vietic-Muong, as opposed to Sino-Xenic words coming from studious application with limited exposure to spoken Sinitic as Sino-Korean and Sino-Japanese have done.^[7]

As a result of a thousand years of Chinese control, a small number of Chinese words were borrowed into Vietnamese, called Old Sino-Vietnamese layer. Furthermore, a thousand years of use of Literary Chinese after independence, a considerable number of Chinese words were borrowed, called the Sino-Vietnamese layer. These layers were first systematically studied by linguist Wang Li.^[8][9]

Middle Chinese and Vietnamese, like most languages of the Mainland Southeast Asia linguistic area, are analytic languages. Almost all morphemes are monosyllabic and lacking inflection. The phonological structure of their syllables is also similar.^[10]

The Old Sino-Vietnamese layer was introduced after the Chinese conquest of the kingdom of Nanyue, including the northern part of Vietnam, in 111 BC. The influence of the Chinese language was particularly felt during the Eastern Han period (25–190 AD), due to increased Chinese immigration and official efforts to sinicize the territory.^[11] This layer consists of roughly 400 words, which have been fully assimilated and are treated by Vietnamese speakers as native words.^[12]

The much more extensive Sino-Vietnamese proper was introduced with Chinese rhyme dictionaries such as the Qieyun in the late Tang dynasty (618–907). Vietnamese scholars used a systematic rendering of Middle Chinese within the phonology of Vietnamese to derive consistent pronunciations for the entire Chinese lexicon.^[13] After driving out the Chinese in 880, the Vietnamese sought to build a state on the Chinese model, including using Literary Chinese for all formal writing, including administration and scholarship, until the early 20th century.^[14] Around 3,000 words entered Vietnamese over this period.^[15][16] Some of these were re-introductions of words borrowed at the Old Sino-Vietnamese stage, with different pronunciations due to intervening sound changes in Vietnamese and Chinese, and often with a shift in meaning.^[13][17]

Wang Li followed Henri Maspero in identifying a problematic group of forms with "softened" initials g-, gi, d- and v- as Sino-Vietnamese loans that had been affected by changes in colloquial Vietnamese. Most scholars now follow André-Georges Haudricourt in assigning these words to the Old Sino-Vietnamese layer.^[23]

Sino-Vietnamese shows a number of distinctive developments from Middle Chinese:

• Sino-Vietnamese distinguishes Early Middle Chinese palatal and retroflex sibilants, which are identified in all modern Chinese varieties, and had already merged by the Late Middle Chinese period.^[24]
• Sino-Vietnamese reflects Late Middle Chinese labiodental initials, which were not distinguished from labial stops at the Early Middle Chinese phase.^[25]
• Middle Chinese grade II finals yield a palatal medial -y- like northern Chinese varieties but unlike southern ones. For example, Middle Chinese 交 kæw yields SV giao, Cantonese gaau and Beijing jiāo.^[26][27]

Up until the early 20th century, Literary Chinese was the vehicle of administration and scholarship, not only in China, but also in Vietnam, Korea and Japan, similar to Latin in medieval Europe.^[28] Though not a spoken language, this shared written language was read aloud in different places according to local traditions derived from Middle Chinese pronunciation: the literary readings in various parts of China and Sino-Xenic pronunciations in the other countries.

As contact with the West grew, Western works were translated into Literary Chinese and read by the literate. In order to translate words for new concepts (political, religious, scientific, medical and technical terminology) scholars in these countries coined new compounds formed from Chinese morphemes and written with Chinese characters. The local readings of these compounds were readily adopted into the respective local vernaculars of Japan, Korea and Vietnam. For example, the Chinese mathematician Li Shanlan created hundreds of translations of mathematical terms, including 代數學 ('replace-number-study') for 'algebra', yielding modern Chinese dàishùxué, Vietnamese đại số học, Japanese daisūgaku and Korean daesuhak.^[29] Often, multiple compounds for the same concept were in circulation for some time before a winner emerged, with the final choice sometimes differing between countries.^[30]

A fairly large amount of Sino-Vietnamese compounds have meanings that differ significantly from their usage in other Sinitic vocabularies. For example:

• bác sĩ (博士) is widely used with the meaning 'physician' or 'medical doctor', while in Chinese it refers to a doctoral degree;
• tiến sĩ (進士) is used to refer to 'doctoral degree', whilst in Chinese it is used to refer to 'successful candidate in the highest imperial civil service examination'.
• bạc 鉑 'silver' is the Old Sino-Vietnamese reflex of Old Chinese *bra:g 白 'white', cognate with later Sino-Vietnamese bạch 'white' and Non-Sino-Vietnamese bệch '(of complexion) chalky',^[31] yet in Chinese 鉑 means 'thin sheet of metal' (variants: 箔, 薄) and 鉑 (pinyin: bó) has also acquired the meaning 'platinum', whose Sino-Vietnamese name is 白金 bạch kim, literally 'white gold';
• luyện kim (煉金) means 'metallurgy' instead of its original meaning, 'alchemy';
• giáo sư (教師) means 'teacher' in Chinese, but is now associated with 'professor' in Vietnamese.
• English "club" became 俱樂部 kurabu in Japan, was borrowed to China, then to Vietnam, is read as câu lạc bộ, and abbreviated CLB, which can be an abbreviation for club.
• linh miêu (靈貓) means 'civet' in Chinese but means 'lynx' in Vietnamese.
• ân nghĩa ~ ơn nghĩa (恩義) not only retains its original Chinese meaning "feeling of gratitude"^[32][33] but also acquires the extended meaning "favor, kindness".^[34]
• thời tiết (時節) is used with the meaning of 'weather", while in Chinese, it means a 'season' (mainly refers to a specific period of time, often within the context of a particular season).
• thư viện (書院) means 'library' in Vietnamese, but in Chinese, it refers to a 'study room' or an 'academy'.
• phương phi (芳菲) is an adjective meaning 'fat' or 'corpulent', but in Chinese, it means 'fragrant' or 'fresh-smelling'.
• ung thư (癰疽) means 'cancer' in Vietnamese, but in Chinese, it is a term used in traditional Chinese medicine meaning a 'skin abscess'.
• thập phân (十分) means 'decimal' in Vietnamese, but in Chinese, it means 'very'; 'extremely'.
• thương (傷) has the meaning 'to like, to love', while also sharing the common meaning of 'to (be) injured, wounded' with Chinese.
• thư (書) refers to a letter, while in Chinese, it means book. (Vietnamese uses sách (冊) instead)

There also a significant amount of Sino-Vietnamese compounds that are used, but the terms differ in Chinese and the other Sino-xenic languages. Such as:

Since Sino-Vietnamese provides a Vietnamese form for almost all Chinese characters, it can be used to derive a Vietnamese form for any Chinese word or name. For example, the name of Chinese leader Xi Jinping consists of the Chinese characters 習近平. Applying Sino-Vietnamese reading to each character yields the Vietnamese translation of his name, Tập Cận Bình.

Some Western names and words, approximated in Chinese or in some cases approximated in Japanese and then borrowed into Chinese, were further approximated in Vietnamese. For example, Portugal is transliterated as Putaoya 葡萄牙 in Chinese, became Bồ Đào Nha in Vietnamese. England (Chinese: Ying-ge-lan) became Anh Cát Lợi (英吉利), shortened to Anh (英), while United States became Mỹ Lợi Gia (美利加), shortened to Mỹ (美). The formal name for the United States in Vietnamese is Hoa Kỳ (花旗); this is a former Chinese name of the United States and translates literally as "flower flag".

Except for the oldest and most deeply ingrained Sino-Vietnamese names, modern Vietnamese instead uses direct phonetic transliterations for foreign names, in order to preserve the original spelling and pronunciation. Today, the written form of such transliterated names are almost always left unaltered; with rising levels of proficiency in English spelling and pronunciation in Vietnam, readers generally no longer need to be instructed on the correct pronunciation for common foreign names. For example, while the Sino-Vietnamese Luân Đôn remains in common usage in Vietnamese, the English equivalent London is also commonplace. Calques have also arisen to replace some Sino-Vietnamese terms. For example, the White House is usually referred to as Nhà Trắng (literally, "white house") in Vietnam, though Tòa Bạch Ốc (based on 白屋) retains some currency among overseas Vietnamese.

However, China-specific names such as Trung Quốc (Middle Kingdom, 中國), as well as Korean names with Chinese roots, continue to be rendered in Sino-Vietnamese rather than the romanization systems used in other languages. Examples include Triều Tiên (Joseon, 朝鮮) for both Korea as a whole and North Korea in particular, Hàn Quốc (Hanguk, 韓國) for South Korea, Bình Nhưỡng (Pyongyang, 平壤), and Bàn Môn Điếm (Panmunjom, 板門店). Seoul, unlike most Korean place names, has no corresponding hanja; it is therefore phonetically transliterated as Xê-un.

This section does not cite any sources. (February 2018)

Sino-Vietnamese words have a status similar to that of Latin-based words in English: they are used more in formal context than in everyday life. Because Chinese and Vietnamese use different order for subject and modifier, compound Sino-Vietnamese words or phrases might appear ungrammatical in Vietnamese sentences. For example, the Sino-Vietnamese phrase bạch mã (白馬 "white horse") can be expressed in Vietnamese as ngựa trắng ("horse white"). For this reason, compound words containing native Vietnamese and Sino-Vietnamese words are very rare and are considered improper by some. For example, chung cư ("apartment building") was originally derived from chúng cư 眾居 ("multiple dwelling"), but with the syllable chúng "multiple" replaced with chung, a "pure" Vietnamese word meaning "shared" or "together". Similarly, the literal translation of "United States", Hợp chúng quốc (合眾國) is commonly mistakenly rendered as Hợp chủng quốc, with chúng (眾 - many) replaced by chủng (種 - ethnicity, race). Another example is tiệt diện (截面; "cross-section") being replaced by tiết diện (節面).

One interesting example is the current motto of Vietnam "Cộng hòa Xã hội chủ nghĩa Việt Nam / Độc lập – Tự do – Hạnh phúc", all the words are Sino-Vietnamese (獨立 – 自由 – 幸福).

Writing Sino-Vietnamese words with the Vietnamese alphabet causes some confusion about the origins of some terms, due to the large number of homophones in Chinese and Sino-Vietnamese. For example, both 明 (bright) and 冥 (dark) are read as minh, thus the word "minh" has two contradictory meanings: bright and dark (although the "dark" meaning is now esoteric and is used in only a few compound words). Perhaps for this reason, the Vietnamese name for Pluto is not Minh Vương Tinh (冥王星 – lit. "underworld king star") as in other East Asian languages, but is Diêm Vương Tinh (閻王星) and sao Diêm Vương, named after the Hindu and Buddhist deity Yama. During the Hồ dynasty, Vietnam was officially known as Đại Ngu (大虞 "Great Peace"). However, most modern Vietnamese know ngu (愚) as "stupid"; consequently, some misinterpret it as "Big Idiot". Conversely, the Han River in South Korea is often erroneously translated as sông Hàn (韓) when it should be sông Hán (漢) due to the name's similarity with the country name. However, the homograph/homophone problem is not as serious as it appears, because although many Sino-Vietnamese words have multiple meanings when written with the Vietnamese alphabet, usually only one has widespread usage, while the others are relegated to obscurity. Furthermore, Sino-Vietnamese words are usually not used alone, but in compound words, thus the meaning of the compound word is preserved even if individually each has multiple meanings.

Today Sino-Vietnamese texts are learnt and used mostly only by Buddhist monks since important texts such as the scriptures to pacify spirits (recited during the ritual for the Seventh Lunar month - Trai đàn Chẩn tế; 齋壇振濟) are still recited in Sino-Vietnamese pronunciations. Such as the chant, Nam mô A Di Đà Phật coming from 南無阿彌陀佛.

• Chữ Nôm (historical writing system modelled on Chinese characters)
• History of writing in Vietnam
• Stratum (linguistics)