As a numeral one
is (cardinal) a numerical value equal to ; the first number in the set of natural numbers (especially in number theory); the cardinality of the smallest nonempty set ordinal: first.
As a pronoun one
) one thing (among a group of others); one member of a group.
As a noun one
is (mathematics) the neutral element with respect to multiplication in a.
As an adjective one
is of a period of time, being particular; as, one morning, one year.
As a verb one
is (obsolete|transitive) to cause to become one; to gather into a single whole; to unite.
As a proper noun united is
(chiefly|british) any of many football teams formed by the amalgamation of smaller ones.