(noun, adjective, verb, pronoun, numeral)


1. used of a single unit or thing; not two or more

Similar word(s): cardinal, ane

2. having the indivisible character of a unit

- spoke with one voice

Similar word(s): united, unitary

3. of the same kind or quality

- two animals of one species

Similar word(s): same

4. (informal) great; used informally as an intensifier

- that is one fine dog

Similar word(s): extraordinary, right

5. indefinite in time or position

- he will come one day

- one place or another

Similar word(s): indefinite

6. being a single entity made by combining separate components

- three chemicals combining into one solution

Similar word(s): combined

7. eminent beyond or above comparison

- she's one girl in a million

- the one and only Muhammad Ali

Similar word(s): incomparable, uncomparable, matchless, nonpareil, peerless, unmatchable, unmatched, unrivaled, unrivalled

Sentences with one as an adjective:

- 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.

- Body and soul are not separate; they are one.

- We are one on the importance of learning.

- The two types look very different, but are one species.

- He is one hell of a guy.

- The town records from 1843 showed the overnight incarceration of one “A. Lincoln”.


1. the smallest whole number or a numeral representing this number

- he has the one but will need a two and three to go with it

- they had lunch at one

Similar word(s): ace, single, unity

Definition categories: quantity, digit, figure

2. a single person or thing

- he is the best one

- this is the one I ordered

Definition categories: thought, unit


1. (cardinal) A numerical value equal to 1; the first number in the set of natural numbers (especially in number theory); the cardinality of the smallest nonempty set. Ordinal: first.

- There is only one God.

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

- One person, one vote.

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


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

- The big one looks good.  I want the green one.  A good driver is one who drives carefully.

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

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

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

- 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.

4. (pronoun) Any person, entity or thing.

- "driver", noun: one who drives.


1. (obsolete, transitive) To cause to become one; to gather into a single whole; to unite.