Thirty/ˈθɜːrti/ Definition 1 of 3Pro Tip 1/3Month Duration Used to express the exact length of certain months in a year. Thirty days make up the month of June. Pro Tip 2/3Age Milestone Represents a significant age for cultural references to adulthood or maturity. He just turned thirty, marking a new chapter in his life. Pro Tip 3/3Time Span Often signifies a considerable amount of time to complete tasks. I'll need thirty minutes to finish this assignment.