Vietnamese numerals

Historically Vietnamese has two sets of numbers: one is etymologically native Vietnamese; the other uses Sino-Vietnamese vocabulary. In the modern language the native Vietnamese vocabulary is used for both everyday counting and mathematical purposes. The Sino-Vietnamese vocabulary is used only in fixed expressions or in Sino-Vietnamese words, in a similar way that Latin and Greek numerals are used in modern English.
For numbers up to one million, native Vietnamese terms are often used the most, whilst mixed Sino-Vietnamese origin words and native Vietnamese words are used for units of one million or above.

Concept

For non-official purposes prior to the 20th century, Vietnamese had a writing system known as Hán-Nôm. Sino-Vietnamese numbers were written in chữ Hán and native vocabulary was written in chữ Nôm. Hence, there are two concurrent systems in Vietnamese nowadays in the romanized script, one for native Vietnamese and one for Sino-Vietnamese.
In the modern Vietnamese writing system, numbers are written as Arabic numerals or in the romanized script chữ Quốc ngữ, which had a chữ Nôm character. Less common for numbers under one million are the numbers of Sino-Vietnamese origin, using chữ Hán. Chữ Hán and chữ Nôm has all but become obsolete in the Vietnamese language, with the Latin-style of reading, writing, and pronouncing native Vietnamese and Sino-Vietnamese being widespread instead, when France occupied Vietnam. Chữ Hán can still be seen in traditional temples or traditional literature or in cultural artefacts. The Hán-Nôm Institute resides in Hanoi, Vietnam.

Basic figures

The following table is an overview of the basic Vietnamese numeric figures, provided in both native and Sino-Vietnamese counting systems. The form that is highlighted in green is the most widely used for all purposes whilst the ones highlighted in blue are seen as archaic but may still be in use. There are slight differences between the Hanoi and Saigon dialects of Vietnamese, readings between each are differentiated below.
Some other features of Vietnamese numerals include the following:

Outside of fixed Sino-Vietnamese expressions, Sino-Vietnamese words are usually used in combination with native Vietnamese words. For instance, mười triệu combines native mười and Sino-Vietnamese triệu.
Modern Vietnamese separates place values in thousands instead of myriads. For example, "123123123" is recorded in Vietnamese as một trăm hai mươi ba triệu một trăm hai mươi ba nghìn một trăm hai mươi ba, or 123 million, 123 thousand and 123. Meanwhile, in Chinese, Japanese & Korean, the same number is rendered as 1億2312萬3123.
*Modern Vietnamese usues comma as decimal separator when written in Arabic numerals.
Sino-Vietnamese numbers are not in frequent use in modern Vietnamese. Sino-Vietnamese numbers such as vạn 'ten thousand', ức 'hundred-thousand' and triệu 'million' are used for figures exceeding one thousand, but with the exception of triệu are becoming less commonly used. Number values for these words are used for each numeral increasing tenfold in digit value, being the number for 10⁵, for 10⁶, et cetera. However, triệu in Vietnamese and 兆 in Modern Chinese now have different values, except for Mainland China, where 兆 is the same-valued SI prefix mega-.

Other figures

Number	chữ Quốc ngữ	Hán-Nôm	Notes
11	mười một
12	mười hai • một tá		Một tá is often used within mathematics-related occasions, to which tá represents the foreign loanword "dozen".
14	mười bốn • mười tư		Mười tư is often used within literature-related occasions, to which tư forms part of the Sino-Vietnamese vocabulary.
15	mười lăm		Here, five is pronounced lăm, or also nhăm by some speakers in the north.
19	mười chín
20	hai mươi • hai chục
21	hai mươi mốt		For numbers which include the digit 1 from 21 to 91, the number 1 is pronounced mốt.
24	hai mươi tư		When the digit 4 appears in numbers after 20 as the last digit of a 3-digit group, it is more common to use tư.
25	hai mươi lăm		Here, five is pronounced lăm.
50	năm mươi • năm chục		When appears after the number 20, the pronunciation changes to mươi.
101	một trăm linh một • một trăm lẻ một		Một trăm linh một is the Northern form, where linh forms part of the Sino-Vietnamese vocabulary; một trăm lẻ một is commonly used in the Southern and Central dialect groups of Vietnam.
1001	một nghìn không trăm linh một • một nghìn không trăm lẻ một		When the hundreds digit is occupied by a zero, these are expressed using không trăm.
10055	mười nghìn không trăm năm mươi lăm

When the number 1 appears after 20 in the unit digit, the pronunciation changes to mốt.
When the number 4 appears after 20 in the unit digit, it is more common to use Sino-Vietnamese tư.
When the number 5 appears after 10 in the unit digit, the pronunciation changes to lăm, or in some Northern dialects, nhăm .
When mười appears after 20, the pronunciation changes to mươi.

Ordinal numbers

Vietnamese ordinal numbers are generally preceded by the prefix thứ-, which is a Sino-Vietnamese word which corresponds to. For the ordinal numbers of one and four, the Sino-Vietnamese readings nhất and tư are more commonly used; two is occasionally rendered using the Sino-Vietnamese nhì. In all other cases, the native Vietnamese number is used.
In formal cases, the ordinal number with the structure "đệ + Sino-Vietnamese numbers" is used, especially in calling the generation of monarches, with an example being Nữ vương Elizabeth đệ nhị, or the Second Spanish Republic being called Đệ nhị Cộng hoà Tây Ban Nha.

Ordinal number	chữ Quốc ngữ	Hán-Nôm
1st	thứ nhất
2nd	thứ hai • thứ nhì
3rd	thứ ba
4th	thứ tư
5th	thứ năm
"n"th	thứ "n"