The anniversary of the day on which a person was born 50 years ago.
1. It's hard to believe she's already celebrating her 50th birthday. 2. He threw a huge party to mark his 50th birthday milestone.
1. "At 50, you have the choice of staying put and coasting or pushing yourself and taking on new challenges." Hillary Clinton, BrainyQuote 2. "Fifty is the age when you can set the pace for the rest of your life." Patrick Duffy, Goodreads