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.

---

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

---

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

Hundreds of Marilyn Monroe’s show up for her birthday.

From MarketWatch • Jun. 2, 2026

Prior to this road trip, the furthest my dog had traveled from home was Mississippi — about two hours away — for a disastrous night in a cabin I’d rented for my ex’s 40th birthday.

From Salon • Jun. 1, 2026

By then, though, the Dodgers had already wrapped the bow on Roberts’ birthday gift.

From Los Angeles Times • May 31, 2026

Congress created an organisation a decade ago to arrange and oversee events commemorating the country's 250th birthday, America250.

From BBC • May 31, 2026

Pop died three years ago, just before my tenth birthday.

From "Code Name Kingfisher" by Liz Kessler