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

Trump is mentioned again on Page 156 of the birthday book document in a photo and a handwritten caption with a crude joke allegedly penned by Joel Pashcow, who the Wall Street Journal reports is a long-time Mar-a-Lago member. —Siladitya Ray, Forbes.com, 9 Sep. 2025

The committee’s subpoena to Epstein’s estate had demanded a wide range of records, including the birthday book, Epstein’s will, his 2008 nonprosecution agreement with federal prosecutors in Florida, and financial documents. —Nik Popli, Time, 9 Sep. 2025

The week prior, Justin and the Rhode founder, 28, celebrated Jack’s first birthday. —Charna Flam, PEOPLE, 9 Sep. 2025

And like many other days, their birthday included a trip to the cemetery. —Jeff Truesdell, People.com, 9 Sep. 2025

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
• astray
• aue
• away
• ballet
• belay
• beltway
• beret

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