Dictionary

The digit or figure 1.

The neutral element with respect to multiplication in a ring.

A one-dollar bill.

One run scored by hitting the ball and running between the wickets; a single.

To cause to become one; to gather into a single whole; to unite.

Of a period of time, being particular.

Example: One day the prince set forth to kill the dragon that had brought terror to his father’s kingdom for centuries.

Being a single, unspecified thing; a; any.

Example: My aunt used to say, "One day is just like the other."

Sole, only.

Example: He is the one man who can help you.

Whole, entire.

Example: Body and soul are not separate; they are one.

The number represented by the Arabic numeral 1; the numerical value equal to that cardinal number.

Example: In many cultures, a baby turns one year old a year after its birth.

The first positive number in the set of natural numbers.

The cardinality of the smallest nonempty set.

The ordinality of an element which has no predecessor, usually called first or number one.

(impersonal pronoun, indefinite) One thing (among a group of others); one member of a group.

Example: Any one of the boys.  The big one looks good.  I want the green one.  A good driver is one who drives carefully.

(impersonal pronoun, sometimes with "the") The first mentioned of two things or people, as opposed to the other.

Example: She offered him an apple and an orange; he took one and left the other.

(indefinite personal pronoun) Any person (applying to people in general).

Example: One’s guilt may trouble one, but it is best not to let oneself be troubled by things which cannot be changed.  One shouldn’t be too quick to judge.

(pronoun) Any person, entity or thing.

Example: "driver", noun: one who drives.