twen·ty / ˈtwentē/ • cardinal number (pl. -ties) the number equivalent to the product of two and ten; ten less than thirty; 20: twenty or thirty years ago twenty of us stood and waited a twenty-foot aerial. (Roman numeral: xx, XX.) ∎ (twenties) the numbers from twenty to twenty-nine, esp. the years of a century or of a person's life: he's in his late twenties. ∎ twenty years old: he's about twenty. ∎ twenty miles an hour. ∎ a size of garment or other merchandise denoted by twenty. ∎ a twenty-dollar bill.DERIVATIVES: twen·ti·eth / -tēi[unvoicedth]/ ordinal numbertwen·ty·fold / -ˌfōld/ adj. & adv.
Twenty questions a parlour game in which a participant has twenty questions (answered by either ‘yes’ or ‘no’) to identify a chosen object. The first recorded reference is in a letter from Hannah More of 1786. In the 20th century, Twenty Questions became the name of a popular radio panel game.
twenty-four seven (usually written 24/7) twenty-four hours a day, seven days a week.
Twenty-six Counties the counties constituting the Republic of Ireland, separated from the Six Counties of Northern Ireland by the peace agreement of 1921–22.
twenty-twenty the Snellen fraction for normal visual acuity, expressed in feet; used informally to denote good eyesight.