歳

Counter for Age

Level 1Sounds Like toshi

Use 歳（さい） after a number to state how old someone is. It is the primary way to express age in Japanese.

How It Works

1. Basic Usage
To state an age, simply place the number before 歳（さい） and follow it with the polite copula. For infants under one year old, ０歳（ぜろさい / れいさい） is used. In casual writing and for children, you will often see 才（さい） used as a shorthand character; while 歳 remains the formal standard, they share the same meaning and reading.

2. Pronunciation & Irregularities
Pay close attention to these specific ages, as they involve sound changes or specific readings:

  • 1 year old: いっさい - Irregular
  • 4 years old: よんさい
  • 7 years old: ななさい (or しちさい)
  • 8 years old: はっさい - Irregular
  • 9 years old: きゅうさい
  • 10 years old: じゅっさい or じっさい - Irregular
  • 20 years old: はたち - Fully Irregular

The sound changes (ending in a small っ) apply to larger numbers ending in 1 and 8, such as 11（じゅういっさい）, 18（じゅうはっさい）, or 21（にじゅういっさい）. They also apply to multiples of 10 up to 90, such as 30（さんじゅっさい） and 40（よんじゅっさい）. Note that 100 is regular: 100歳（ひゃくさい）.

For 20 years old, はたち is the cultural and conversational standard used in daily life. Because it is a special word, it stands alone—never say はたちさい. However, にじゅっさい is also used, particularly in formal, technical, or legal contexts.

3. Asking for Age
To ask someone's age, you can use 何歳（なんさい）ですか. To be more polite (especially with superiors or strangers), use the phrase おいくつですか. When asking a direct question about age, it is common to soften it with a cushion phrase like 失礼（しつれい）ですが (Excuse me, but...). In casual situations, you can simply ask いくつ？ or 何歳（なんさい）？.

Examples (4)

  1. 私は二十五歳です。

    I am 25 years old.

    Word by Word: I (topic) 25-years-old am.

    A standard way to introduce your age using the topic marker and polite copula.

  2. 弟は二十歳（はたち）です。

    My younger brother is twenty years old.

    Word by Word: Younger brother (topic) twenty-years-old is.

    This uses the irregular reading はたち for age 20, which is a significant milestone in Japan.

  3. うちの犬は今年で八歳（はっさい）になります。

    Our dog will turn eight this year.

    Word by Word: Our dog (topic) this year by eight-years-old (target) becomes.

    Note the irregular pronunciation はっさい for 8 years old. The counter is used for animals as well as humans.

  4. 田中さんの娘さんは一歳（いっさい）です。

    Mr. Tanaka's daughter is one year old.

    Word by Word: Tanaka-san's daughter (topic) one-year-old is.

    Note the irregular pronunciation いっさい for 1 year old.

Common Mistakes

  • Using 歳（さい） for the age of inanimate objects like buildings or wine.

    このビルは五十歳です。
    このビルは築五十年です。

    歳（さい） is only for living beings. For buildings, use 築（ちく）...年（ねん） or simply the counter for years, 年（ねん）.

  • Pronouncing 1 year old or 8 years old literally without the small っ sound change.

    いちさい / はちさい
    いっさい / はっさい

    Numbers ending in 1, 8, and multiples of 10 up to 90 undergo a sound change (gemination) when combined with 歳（さい）.

  • Adding 歳（さい） to the special word for 20 years old, はたち.

    私ははたちさいです。
    私ははたちです。

    The word 二十歳（はたち） is a special, standalone term for 20 years old. Because the concept of age is already built into the word, you should never add the counter 歳（さい） to it.

How It Connects

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

歳Level 1Counter for Age

Learn This First

To use the age counter 歳, you need to understand basic kanji for the character itself, how to use the copula 'desu' to form a complete sentence about age, and how to use the question word 'nan' to ask for someone's age.

Words in This Pattern

歳