A birthday is the date on which a person was born. It is customary in many cultures to celebrate the anniversary of one's birthday in some way, for example by having a birthday party.
One traditional (USA) song to sing to someone at such a party is "Happy Birthday", particularly while bringing a birthday cake into the room, covered with lit candles. The person whose birthday it is will then make a wish and if they blow out the candles in one breath it's supposed to come true.
People often get (and give!) gifts on their birthday.
Astrological signs typically depend on one's birthday, or even the specific time of birth.
Notable birthdays can include:
- When the most significant digit changes, for example one's 1st, 10th, 20th, 50th, or 100th birthdays.
- In most legal systems, one becomes a legal adult on a particular birthday, and at different ages gain different rights and responsibilities -- voting, certain drug use (e.g. alcohol, tobacco), eligibility for military draft, etc.
- Most cultures have one or more coming of age birthdays:
- Jewish girls have a bat mitzvah on their 12th birthday; Jewish boys have a bar mitzvah on their 13th.
- Many girls in the USA have "sweet sixteen" birthday parties.
- In many countries it is traditional when it becomes legal for you to drink for your older friends to drag you out to bars and get you rip-roaring drunk.