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

Fifty years ago this weekend, America celebrated its 200th birthday. — Steve Bousquet, Sun Sentinel, 4 July 2026

Both West Point and the United States Air Force Academy have ensured Ben’s story will continue to live on for many more years of America’s birthday. — Doug Melville, Forbes.com, 4 July 2026

During that trip, Prince Harry and Meghan celebrated their daughter's first birthday with a backyard party at Frogmore Cottage, their former residence, and released an official photo of Lili from the event. — Simon Perry, PEOPLE, 4 July 2026

Despite triple-digit heat indexes, visitors from across the country gathered in Philadelphia today to celebrate the nation's 250th birthday at the birthplace of American independence. — Kyla Guilfoil, NBC news, 5 July 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