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

There’s excitement and chaos in equal measures, like the first 15 minutes of a children’s birthday party.

From The Wall Street Journal • Jun. 10, 2026

Assuming 7% growth, that could grow to roughly $180,000 by the child’s 18th birthday.

From MarketWatch • Jun. 9, 2026

Jennings was having a birthday party with family that day, according to court documents.

From Los Angeles Times • Jun. 9, 2026

Trump still has several high-wattage events on his summer calendar, namely an Ultimate Fighting Championship match in a massive structure on the South Lawn set for his 80th birthday Sunday.

From The Wall Street Journal • Jun. 9, 2026

Mutti and Karli had made me a birthday card, and gave it to me at breakfast.

From "An Elephant in the Garden" by Michael Morpurgo