noun
birthday
BURTH-day
noun
1
The yearly anniversary of the day someone was born.
"They threw her a huge party for her thirtieth birthday."
"What do you want for your birthday this year?"
2
The anniversary of when something (a company, a country, etc.) was founded.
"The museum celebrated the birthday of the national park."
How to Use Birthday
Learner’s notesIn plain EnglishThe date each year that marks when you (or something) came into being.
Common pairings
happy birthday
birthday party
birthday present
turn (a number) on your birthday
Word Forms
birthdayed past tense, birthdays plural, birthdays singular
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They threw her a huge party for her thirtieth _____.
Etymology
From Old English gebyrddæg, a compound of "birth" and "day" — literally "day of birth".