- (US) thousand one, one thousand one, a thousand one
- (UK) thousand and one, one thousand and one, a thousand and one
- Arabic numerals: 1001. Roman numerals: MI
- (US) One thousand plus one.
- (informal) The ordinality of an element whose predecessor is thousandth; usually called thousand-first (US) or thousand-and-first (UK) but sometimes number thousand one (US) or number thousand and one (UK).
- (informal) A great number.
- I have a thousand and one things to do today.
one thousand plus one