—n. (pl. -ies)
1 the product of two and ten.
2 a symbol for this (20, xx, XX).
3 (in pl.) the numbers from 20 to 29, esp. the years of a century or of a person's life.
4 colloq. a large indefinite number (have told you twenty times).
—adj. that amount to twenty.
Phrases and idioms:
twenty-first, -second , etc. the ordinal numbers between twentieth and thirtieth. twenty-one, -two , etc. the cardinal numbers between twenty and thirty. twenty-twenty (or 20/20)
1 denoting vision of normal acuity.
2 colloq. denoting clear perception or hindsight.
Derivatives:
twentieth adj. & n. twentyfold adj. & adv.
Etymology: OE twentig (perh. as TWO, -TY(2))
Useful english dictionary. 2012.