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

Yet and The Real O'Neals, first met in 2019, when they were introduced at a mutual friends' 50th birthday party. —Ryan Coleman, Entertainment Weekly, 27 Oct. 2025

Last October, the singer and songwriter indefinitely delayed her second studio album after her book of songs slated for the record were taken in a car theft just ahead of her birthday. —Larisha Paul, Rolling Stone, 27 Oct. 2025

That December, Tavia put in a request for Swift's birthday present packaging. —Zoey Lyttle, PEOPLE, 27 Oct. 2025

Avoid posting sensitive information like travel plans, birthdays or financial updates on social media. —Kurt Knutsson, FOXNews.com, 14 Oct. 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