mốt

One in Twenty-One and Up

Level 1

When counting from 21 upwards, the number 1 changes its pronunciation from một to mốt.

How It Works

When building numbers in Vietnamese, the number 1 is usually một. However, when it sits in the ones place and the tens digit is 2 or higher, it changes to mốt. This rule also applies to ordinal numbers (e.g., thứ hai mươi mốt for 21st).

  • 21 = hai mươi mốt
  • 31 = ba mươi mốt
  • 91 = chín mươi mốt

Important Exceptions:

  • 11 is mười một (because the tens digit is 1).
  • 101 is một trăm lẻ một (or một trăm linh một in the North) (because the tens digit is 0).

Listening & Speaking Tips:

  • In daily speech, the word mươi is frequently dropped. For example, 21 becomes hai mốt instead of hai mươi mốt.
  • In casual speech, 21 is often contracted to hăm mốt and 31 to băm mốt.
  • You will often hear people say một trăm mốt. Be careful! This is a common shorthand for 110 (một trăm mười), not 101. This shorthand pattern also extends to other multipliers like hai trăm mốt (210), larger numbers like một ngàn mốt (1,100) and một triệu mốt (1,100,000), and even measurements or money, such as một ký mốt (1.1 kg).
  • When reading numbers digit-by-digit (like phone numbers, bus numbers, or room numbers), the number 1 remains một. For example, a phone number ending in 2-1 is read as hai một, not hai mốt.

Note: You might also see the word mốt used to mean 'fashion/trend' (from French 'mode'), 'the day after tomorrow' (in Southern and Central dialects, whereas Northerners use ngày kia for the day after tomorrow and ngày kìa for three days from now, and do not natively use mốt as a time word), or in the phrase mai mốt (in the near future), but these are completely different words.

Examples (4)

  1. Lớp tôi có hai mươi mốt học sinh.

    My class has twenty-one students.

    Word by Word: Class my have two ten one student.

    Notice how 21 uses 'mốt' instead of 'một'.

  2. Năm nay bà ấy tám mươi mốt tuổi.

    She is eighty-one years old this year.

    Word by Word: Year this grandmother that eight ten one age.

    For 81, the tens digit is 8, so the rule applies.

  3. Cái áo này giá hai trăm ba mươi mốt nghìn.

    This shirt costs 231 thousand.

    Word by Word: Object shirt this price two hundred three ten one thousand.

    Even in larger numbers like 231, the final two digits dictate the use of 'mốt'.

  4. Tháng này có ba mươi mốt ngày.

    This month has thirty-one days.

    Word by Word: Month this have three ten one day.

    31 uses 'mốt'.

Common Mistakes

  • Using 'mốt' for 11 or 101.

    Tôi có mười mốt quyển sách.
    Tôi có mười một quyển sách.

    The rule for 'mốt' only applies when the tens digit is 2 through 9. For 11, the tens digit is 1, so it remains 'mười một'.

  • Thinking 'một trăm mốt' means 101.

    Phòng một trăm mốt là phòng 101.
    Phòng một trăm lẻ một là phòng 101.

    'Mốt' only replaces 'một' after a tens word like 'hai mươi' (hai mươi mốt = 21), so it cannot stand for the 1 in 101. To say 101, say 'một trăm lẻ một' (or 'một trăm linh một' in the North).

How It Connects

Tap a pattern to see what it builds on and what it leads to.

mốtLevel 1One in Twenty-One and Up

Learn This First

To understand why 'một' changes to 'mốt', you first need to understand the basic counting system and how the word 'mươi' is used to form the tens place for numbers 20 through 90.

Words in This Pattern

mốt