Twenty/ˈtwenti/ Definition 1 of 2Pro Tip 1/3Round Number Twenty is often used to describe even, round quantities, like prices or ages. The jacket costs twenty dollars, not nineteen or twenty-one. Pro Tip 2/3Measurement Units Add the unit of measure after 'twenty' to clarify what you are counting. Please wait twenty minutes. Pro Tip 3/3Cultural Milestone Turning twenty is often seen as a significant milestone in many cultures. My sister had a big party when she turned twenty.