Sixteenth/ˌsɪksˈtiːnθ/ Definition 1 of 4Pro Tip 1/3Ordinal Usage Used to show the order of things in a sequence; often in dates and lists. She finished sixteenth in the race. Pro Tip 2/3Historical Periods Reference to centuries when talking about history or classical topics. Shakespeare lived during the sixteenth century. Pro Tip 3/3Birthday Milestone Marks significant age milestones in many cultures, especially turning 16. Her sixteenth birthday was a huge celebration.