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

That model was approved by the NCAA Division I Cabinet in June and provides five years of eligibility beginning at the start of the academic year following an athlete’s 19th birthday or upon fulltime enrollment in college, whichever comes sooner. — Michael McCann, Sportico.com, 5 Oct. 2026

Kimball, 63, was adopted on his first birthday by a family in Berkeley after spending a few months in the foster care system. — Stephen Hobbs, Sacbee.com, 5 Oct. 2026

As for the lingering question over Mary and Robert’s ambiguous glance at the end of the finale as the two were seen celebrating the birthday of Mary’s daughter together, that may be answered in Season 2 with a reference of the characters’ status. — Nellie Andreeva, Deadline, 5 Oct. 2026

Star67, a private-dining concept, kept the crowd snacking on birthday cake bites and ice cream sundaes as the drinks flowed. — Ryma Chikhoune, Footwear News, 5 Oct. 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