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

Sir David Attenborough has said he has been "completely overwhelmed" by the messages he has received ahead of his 100th birthday.

From BBC • May 7, 2026

Grounding these dramatic acrobatics is that tree, which we first meet a decade or so shy of its 200th birthday, in a section set just before and then during the Covid-19 pandemic.

From The Wall Street Journal • May 7, 2026

Argentine scientists analysed samples from most of the 33 infected people, which included 11 deaths, during the outbreak in Epuyen, and reconstructed how people crossed paths at that fateful birthday party.

From Barron's • May 7, 2026

On the Angels’ broadcast the previous night, reporter Erica Weston presented play-by-play announcer Wayne Randazzo with a birthday gift: a figurine of Grogu, a character in the Star Wars family.

From Los Angeles Times • May 7, 2026

“Let me ask you something. How come all of Fernlight Forest is talking about a half-dead fox who showed up to Ragginold’s birthday looking for information about his long-gone mommy?”

From "The Undead Fox of Deadwood Forest" by Aubrey Hartman