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

If your husband is still with us on this 80th birthday, you can revisit your calculations then.

From MarketWatch • Jun. 9, 2026

Directed by Craig Gillespie, “Supergirl” will follow the eponymous Kryptonian as she is celebrating her 23rd birthday.

From Los Angeles Times • Jun. 9, 2026

Sarah Kellen told the US House Oversight Committee that they were also present at Princess Beatrice's 18th birthday party at Windsor Castle in 2006.

From BBC • Jun. 8, 2026

It turned out that even as he approached his 40th birthday, his soccer career wasn’t quite dead yet.

From The Wall Street Journal • Jun. 6, 2026

“Can we reschedule this debate? It is my birthday, after all,” I point out.

From "Split the Sky" by Marie Arnold