birthday

American  

[burth-dey] / ˈbɜrθˌdeɪ /

noun

1. the anniversary of a birth.

2. the day of a person's birth.

3. a day marking or commemorating the origin, founding, or beginning of something.

4. the festivities or celebration marking such a day or anniversary.

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birthday British  

/ ˈbɜːθˌdeɪ /

noun

1. 1. an anniversary of the day of one's birth

   2. ( as modifier )

      birthday present

2. the day on which a person was born

3. any anniversary

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Etymology

Origin of birthday

Middle English word dating back to 1350–1400; see origin at birth, day

Explanation

Your birthday is the day of your birth! It’s the yearly anniversary that marks the day you were born. Not everyone celebrates, but a birthday is a good excuse for a party and cake. You can use birthday both to refer to the specific day of a baby's birth, and the annual marking of that day throughout the years that follow. Sometimes people talk about the birthday of a country, group, or even a building: "It's the art museum's fiftieth birthday next year." The Old English byrddæg originally referred to the celebration of a king or saint's birth, but over the years it was extended to include everyone.

Example Sentences

I stopped celebrating half-birthdays decades ago, but today is my 54½ birthday — and it’s a significant milestone because I’ve decided to retire in exactly five years.

From MarketWatch • Apr. 22, 2026

Apple celebrated its 50th birthday at Grand Central Station in New York City a few weeks ago.

From The Wall Street Journal • Apr. 21, 2026

That performance is one of two concerts highlighting the work of the New York minimalist as he celebrates his 90th birthday.

From BBC • Apr. 20, 2026

I’ve celebrated my birthday at a go-kart racing track and a bowling alley.

From Los Angeles Times • Apr. 20, 2026

Ana knows it’s my birthday, but no one else does because it feels weird to announce.

From "The Tenth Mistake of Hank Hooperman" by Gennifer Choldenko