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The cardinal number equivalent to the product of two and ten; ten less than thirty; 20. Recorded from Old English (in form twentig) the word comes from the base of two + -ty.

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.

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