Other forms: birthdays
Your birthday is the day each year when you turn a year older. Happy birthday, a birthday card, my birthday is in June.
It takes on for a date — on my birthday — and in for a month. Birthday card, birthday cake, birthday present and birthday party are the standard compounds. Note in your birthday suit, meaning naked; birthday honours, the British list published for the monarch's official birthday; and that the birthday problem in probability is the surprising fact that in a room of twenty-three people two probably share one.
1nounbirthdayThe day each year when somebody turns a year older.
“Her birthday is in June and everybody forgets.”
birthday is an annual date.
Old English gebyrddaeg is birth plus day, both native words. It is one of the plainest compounds in English and has been in continuous use for well over a thousand years.
Old English
ġebyrddæġ
Middle English
birthdai
English, today
birthday
From Middle English birthdai, from Old English ġebyrddæġ. From Middle English birthdai, birtheday, from Old English ġebyrddæġ (“birthday”), influenced by Old Norse burðr, equivalent to birth + day. Compare stq Gebuursdai (“birthday”), Dutch geboortedag (“birthday”), Low German Geboortsdag (“birthday”), German Geburtstag (“birthday”), Norwegian bursdag, gebursdag (“birthday”). Eclipsed non-native Middle English nativitee (“birth, nativity, birthday”), from Old French nativité, nativited, from Latin nātīvitas.
Etymology from Wiktionary, CC BY-SA