one

Definitions
Examples

(noun): The digit or figure 1.
(noun): The neutral element with respect to multiplication in a ring.
(noun): A one-dollar bill.
(noun): One run scored by hitting the ball and running between the wickets; a single.
(noun): A joke or amusing anecdote.
(noun): A particularly special or compatible person or thing.
(noun): (leet) Used instead of ! to amplify an exclamation, parodying unskilled typists who forget to press the shift key while typing exclamation points, thus typing "1".
(verb): To cause to become one; to gather into a single whole; to unite.
(adjective): Of a period of time, being particular.
(adjective): Being a single, unspecified thing; a; any.
(adjective): Sole, only.
(adjective): Whole, entire.
(adjective): In agreement.
(adjective): The same.
(adjective): Being a preeminent example.
(adjective): Being an unknown person with the specified name; see also "a certain".
(numeral): The number represented by the Arabic numeral 1; the numerical value equal to that cardinal number.
(numeral): The first positive number in the set of natural numbers.
(numeral): The cardinality of the smallest nonempty set.
(numeral): The ordinality of an element which has no predecessor, usually called first or number one.
(pronoun): (impersonal pronoun, indefinite) One thing (among a group of others); one member of a group.
(pronoun): (impersonal pronoun, sometimes with "the") The first mentioned of two things or people, as opposed to the other.
(pronoun): (indefinite personal pronoun) Any person (applying to people in general).
(pronoun): (pronoun) Any person, entity or thing.

I knew as soon I met him that John was the one for me and we were married within a month.
2003 September 26, "DEAL WITH IT!!!!11one!!", in alt.games.video.nintendo.gamecube, Usenet
One day the prince set forth to kill the dragon that had brought terror to his father’s kingdom for centuries.
My aunt used to say, "One day is just like the other."
He is the one man who can help you.