birthday

noun

birth·​day ˈbərth-ˌdā 

1

a

: the day of a person's birth

b

: a day of origin

2

: an anniversary of a birth

her 21st birthday

Examples of birthday in a Sentence

Her birthday is September 30th.

Today is his 21st birthday.

The company just celebrated its 50th birthday.

Recent Examples on the Web

The whole crew, minus Jason, who can’t bend his knee, and Lacy, who needs a whole day to get to an airport owned by John Wayne, goes to Punta Mita, Mexico, to celebrate the birthdays of Schwartz, Zack, and Danny. —Brian Moylan, Vulture, 18 June 2026

Lucy passed away just a month before her second birthday from a brain hemorrhage — cancer-free. —Siafa Lewis, CBS News, 17 June 2026

Contractors would be responsible for sandblasting, caulking and resurfacing the pool basin, the president told reporters on May 7, as part of an initiative to beautify Washington before the country's 250th birthday. —Michelle Del Rey, USA Today, 17 June 2026

With beach vacations, girls' trips, and birthdays on the horizon, there's plenty to prepare for. —Amanda Le, InStyle, 17 June 2026

Word History

First Known Use

14th century, in the meaning defined at sense 2

Phrases Containing birthday

• birthday suit

Rhymes for birthday

• airway
• allay
• archway
• array
• ashtray
• assez
• astray
• aue
• away
• ballet
• belay
• beltway

Kids Definition

birthday

noun

birth·​day ˈbərth-ˌdā 

1

: the day or anniversary of one's birth

2

: the day or anniversary of a beginning