twenty

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The cardinal number equal to 2 × 10.
• noun A decade or the numbers from 20 to 29.
• noun The decade from 20 to 29 in a century.
• noun A twenty-dollar bill.

from The Century Dictionary.

• One more than nineteen; twice ten: a cardinal numeral.
• Proverbially, an indefinite number: sometimes duplicated.
• noun The number which is one more than nineteen; twice ten; a score.
• noun A symbol rep resenting this number, as 20, XX, or xx.
• noun An old division of English infantry (see thousand and hundred). The commander of a twenty was called vintiner.

from the GNU version of the Collaborative International Dictionary of English.

• noun The number next following nineteen; the sum of twelve and eight, or twice ten; twenty units or objects; a score.
• noun A symbol representing twenty units, as 20, or xx.
• adjective One more than nineteen; twice ten.
• adjective An indefinite number more or less that twenty.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The cardinal number 20, occurring after nineteen and before twenty-one.
• noun colloquial A banknote with a denomination of 20.
• noun 10-20 (location).
• noun military A set of twenty push-ups.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective denoting a quantity consisting of 20 items or units
• noun the cardinal number that is the sum of nineteen and one
• noun a United States bill worth 20 dollars