A birthday is the anniversary of the birth of a person, or figuratively of an institution. Birthdays of people are celebrated in numerous cultures, often with birthday gifts, birthday cards, a birthday party, or a rite of passage.
Many religions celebrate the birth of their founders or religious figures with special holidays (e.g. Christmas, Mawlid, Buddha's Birthday, and Krishna Janmashtami).
There is a distinction between birthday and birthdate: The former, other than February 29, occurs each year (e.g. January 15), while the latter is the exact date a person was born (e.g., January 15, 2001).
the year, month, and day of someone's birth; date of birth
The anniversary of the day on which someone is born. From 1570s
The anniversary of the day on which something is created.
The date on which someone is born or something is created, more commonly called birthdate or date of birth.
To celebrate one's birthday.
the anniversary of the day on which a person was born, typically treated as an occasion for celebration and the giving of gifts
"his twenty-ninth birthday"
"a birthday cake"
the day of a person's birth
"he shares a birthday with Rod Stewart"
the anniversary of something's origin or foundation
"the seventy-fifth birthday of the Institute"
The day in which any person is born; day of origin or commencement.
The day of the month in which a person was born, in whatever succeeding year it may recur; the anniversary of one's birth.
Of or pertaining to the day of birth, or its anniversary; as, birthday gifts or festivities.
an anniversary of the day on which a person was born (or the celebration of it)
the date on which a person was born