How to Say "Birthdays" in Japanese

誕生日

tanjōbi[tã̠ɲ̟d͡ʑo̞ːbʲi]

The English phrase 'birthdays' is translated into Japanese as 誕生日 (tanjōbi).

誕生日 refers to the anniversary of the day a person was born.

How does it change in a sentence?

Japanese nouns do not change form to indicate plurality, so 誕生日 is used for both 'birthday' and 'birthdays'.

tanjōbi

In Japan, some people still use the 'kazoedoshi' system, where everyone is one year old at birth and turns a year older on New Year's Day rather than their 誕生日.
In Japan, it is common to use the term 誕生日会 (tanjōbi-kai) to describe a birthday party, which literally translates to a 'birthday meeting'.
The word 誕生日 contains a linguistic phenomenon called rendaku, where the sound of the second word shifts from 'hi' to 'bi' to make the compound easier to pronounce smoothly.

誕生日って大事だと思う？
Do you feel birthdays are important?
This sentence uses 誕生日 to ask about the importance of birthdays.
Tatoeba #2298534 by tommy_san, translation #953185 by CK
トムと私の誕生日はたった１日しか違わないのに、トムの方が学年が上なのよ。
Even though our birthdays are only one day apart, Tom is one year ahead of me in school.
This sentence uses 誕生日 to compare two different birthdays.
Tatoeba #10640479 by small_snow, translation #10768233 by CK
誕生日は大事だと思います。
I think birthdays are important.
This sentence uses 誕生日 to express an opinion on the importance of birthdays.
Tatoeba #4203401 by Sereptie, translation #3728527 by CM
2 more sentences on Tatoeba

Yota and Yui are talking about their schedules.

陽太 Yota

結衣さんの誕生日はいつですか？
Yui-san no tanjōbi wa itsu desu ka?
When is your birthday, Yui?
結衣 Yui

私の誕生日は来月の十日です。
Watashi no tanjōbi wa raigetsu no tōka desu.
My birthday is the tenth of next month.
陽太 Yota

そうなんですね！何か計画はありますか？
Sō nan desu ne! Nanika keikaku wa arimasu ka?
I see! Do you have any plans?
結衣 Yui

まだ何も決めていません。
Mada nanimo kimete imasen.
I haven't decided anything yet.

Sources

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