Numbers, Age, and Telephone Numbers

Base Numbers: 0 to 10

Mastering numbers is an essential foundation for daily Japanese communication. The numbers from zero to ten form the building blocks for all higher numbers, time expressions, and counting systems. In Japanese, zero is commonly read as ゼロ (zero), though you may also hear れい (rei) in formal contexts. The numbers 1 through 10 are: 1 一 (ichi), 2 二 (ni), 3 三 (san), 4 四 (yon or shi), 5 五 (go), 6 六 (roku), 7 七 (nana or shichi), 8 八 (hachi), 9 九 (kyuu or ku), and 10 十 (juu).

Notice that the numbers 4, 7, and 9 possess multiple readings. Four is usually よん (yon), but can be pronounced し (shi). However, because し sounds identical to the Japanese word for death (死, shi), speakers often avoid it when counting or giving phone numbers. Seven is pronounced either なな (nana) or しち (shichi), with なな being preferred in phone numbers to avoid confusion with いち (ichi). Nine is read as either きゅう (kyuu) or く (ku). Learning both sets of readings will help you recognize them in different contexts.

Counting Beyond Ten: 11 to 99

Forming numbers from 11 through 99 is straightforward because Japanese uses a logical base-10 combination system. To make numbers from 11 to 19, simply take 十 (juu, 10) and add the single digit. For instance, 11 is 十一 (juu-ichi), 12 is 十二 (juu-ni), 14 is 十四 (juu-yon), and 19 is 十九 (juu-kyuu).

To express multiples of ten, place the multiplier before 十 (juu). For example, 20 is 二十 (ni-juu, literally 'two tens'), 30 is 三十 (san-juu), 50 is 五十 (go-juu), and 80 is 八十 (hachi-juu). Notice that 40 is 四十 (yon-juu), 70 is 七十 (nana-juu), and 90 is 九十 (kyuu-juu)—retaining the safer, preferred readings. To form compound numbers such as 47, simply chain the parts together: 40 + 7 becomes yon-juu nana (よんじゅうなな).

Giving and Asking for Telephone Numbers

In Japan, telephone numbers are written with hyphens separating the area code, exchange, and subscriber number, such as 090-1234-5678. When reading a phone number aloud, the hyphen is pronounced as the particle の (no). This particle links the number segments and signals a brief pause to the listener, making the digits easier to follow and write down.

When reciting digits, use ゼロ (zero) for 0, よん (yon) for 4, and なな (nana) for 7 to maximize clarity over the line. For example, the number 03-3456-7890 is read aloud as: 'ゼロ・さん・の・さん・よん・ご・ろく・の・なな・はち・きゅう・ゼロ' (zero-san no san-yon-go-roku no nana-hachi-kyuu-zero).

To ask someone for their phone number, use the question pattern: 電話番号は何番ですか (Denwa bangou wa nanban desu ka?), which translates to 'What is your telephone number?'. To answer, state your number followed by です (desu): '090-1234-5678 です' (zero-kyuu-zero no ichi-ni-san-yon no go-roku-nana-hachi desu).

Expressing Age with the Counter 〜歳 (sai)

In Japanese, items and concepts cannot usually be counted with bare numbers; they require specific counter suffixes. For age, the counter suffix is 歳 (sai), often simplified as 才 in everyday handwriting. In general, you state a person's age by adding さい (sai) directly after the number: 二歳 (ni-sai, 2 years old), 三歳 (san-sai, 3 years old), and 五歳 (go-sai, 5 years old).

However, age involves several important sound contractions (促音, sokuon) that occur when combining digits with 'sai'. One year old is not 'ichi-sai', but いっさい (issai). Eight years old contracts to はっさい (hassai), and ten years old becomes じゅっさい (jussai, or alternatively じっさい, jissai). These contractions recur in compound ages ending in those numbers; for example, 28 years old is にじゅうはっさい (nijuuhassai).

The most famous exception in Japanese age counting is 20 years old. Historically considered the traditional age of majority, 20 years old is called はたち (hatachi). Notice that はたち does not use the counter さい (sai) at all; saying 'ni-juu-sai' is occasionally understood, but はたち is the standard, culturally preferred term.

Asking Age and Common Conversational Phrases

To ask someone's age in a casual or standard polite setting, ask 何歳ですか (Nan-sai desu ka?). The word 何 (nan) means 'what' or 'how many', so this literally asks 'How many years old are you?'. When speaking to someone older, a superior, or a customer, use the more polite and respectful phrase おいくつですか (O-ikutsu desu ka?).

Responding is simple: state your age followed by the polite copula です (desu). For example, a 23-year-old would say: '二十三歳です' (Nijuusan-sai desu). If you want to introduce yourself with your name and age together, you can say: '初めまして。田中です。二十歳です。どうぞよろしくお願いします。' (Hajimemashite. Tanaka desu. Hatachi desu. Douzo yoroshiku onegaishimasu. - Nice to meet you. I am Tanaka. I am 20 years old. Pleased to meet you.).