one \one\, n.
   1. a single unit; as, one is the base of all numbers.
      1913 webster

   2. a symbol representing a unit, as 1, or i.
      1913 webster

   3. a single person or thing. "the shining ones." --bunyan.
      "hence, with your little ones." --shak.
      1913 webster

            he will hate the one, and love the other. --matt.
                                                  vi. 24.
      1913 webster

            that we may sit, one on thy right hand, and the
            other on thy left hand, in thy glory. --mark x. 37.
      1913 webster

   after one, after one fashion; alike. obs. --chaucer.

   at one, in agreement or concord. see at one, in the
      vocab.

   ever in one, continually; perpetually; always. obs.
      --chaucer.

   in one, in union; in a single whole.

   one and one, one by one, singly; one at a time; one after
      another. "raising one by one the suppliant crew."
      --dryden.

   one on one contesting an opponent individually; -- in a
      contest.

   go one on one, to contest one opponent by oneself; -- in a
      game, esp. basketball.
      1913 webster +pjc
see also:
after one at one ever in one in one one and one one by one 
one on one go one on one