birthday

American

[burth-dey] / ˈbɜrθˌdeɪ /

noun

the anniversary of a birth.
the day of a person's birth.
a day marking or commemorating the origin, founding, or beginning of something.
the festivities or celebration marking such a day or anniversary.

birthday British

/ ˈbɜːθˌdeɪ /

noun

1. an anniversary of the day of one's birth
2. ( as modifier )
  
  birthday present
the day on which a person was born
any anniversary

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of birthday

Middle English word dating back to 1350–1400; birth, day

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

The company, which celebrated its 50th birthday this week, was started by two Steves in a San Franciscan garage.

From BBC • Apr. 4, 2026

“It’d be the ultimate 60th birthday present, right?” she said.

From Los Angeles Times • Apr. 4, 2026

Many of them were asleep after celebrating till midnight at a birthday party.

From The Wall Street Journal • Apr. 1, 2026

Nobody has set foot on the moon since 1972, the year Musk celebrated his first birthday.

From MarketWatch • Mar. 31, 2026

Then Sal, the one I’d met in town, asked if I was going to Karly’s birthday party.

From "Code Name Kingfisher" by Liz Kessler

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023