The day on which a person was born; often used for celebrating that day each year.
来週は私の誕生日だから、友だちがパーティーを開いてくれるらしい。
My birthday is next week, so my friends say they'll throw a party for me.
母は毎年家族で父の誕生日を祝うのが習慣だ。
My mother has a habit of the family celebrating my father's birthday every year.
子どもたちは学校で友だちの誕生日カードを作った。
The children made birthday cards for a friend at school.
誕生日プレゼントは何がいいか、まだ決めていない。
I haven't decided what would be a good birthday present yet.