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

Sedaka himself became a star through such bright confections as “Calendar Girl,” “Happy Birthday, Sweet Sixteen” and “Breaking Up Is Hard to Do,” the 1962 chart-topper that became his signature song.

From Los Angeles Times • Feb. 27, 2026

Presidents Day isn’t even officially called Presidents Day: It is designated by U.S. law as Washington’s Birthday and was created in 1885 to honor President George Washington.

From Barron's • Feb. 16, 2026

It originally marked the birthday of our first president, George Washington, and is still designated as Washington’s Birthday on the federal and New York Stock Exchange calendars.

From MarketWatch • Feb. 13, 2026

Appeared in the December 8, 2025, print edition as 'Jimmy Lai’s Birthday Gift—to China'.

From The Wall Street Journal • Dec. 7, 2025

The Greatest Birthday Ever was back on track.

From "Eleven" by Tom Rogers