I. | ̷ ̷ ̷ ̷| ̷ ̷ adjective
: being one more than 20 in number
twenty-one years
— see number table
II. pronoun, plural in construction
: 21 countable persons or things not specified but under consideration and being enumerated
twenty-one are here
twenty-one were found
III. noun
1. : one and 20 : three times seven
2.
a. : 21 units or objects
a total of twenty-one
b. : a group or set of 21
3. : the numerable quantity symbolized by the arabic numerals 21
4. : the 21st in a set or series ; especially : an article of clothing of the 21st size
wear a twenty-one
5. or 21
[translation of French vingt-et-un ]
: a card game the object of which is to be dealt cards having a higher count than those of the dealer up to but not exceeding 21 — called also blackjack, vingt-et-un