between you and me
  只有我們兩人知道,不能讓其他人知道
  Be·tween prep.
  1. In the space which separates; betwixt; as, New York is between Boston and Philadelphia.
  2. Used in expressing motion from one body or place to another; from one to another of two.
     If things should go so between them.   --Bacon.
  3. Belonging in common to two; shared by both.
     Castor and Pollux with only one soul between them.   --Locke.
  4. Belonging to, or participated in by, two, and involving reciprocal action or affecting their mutual relation; as, opposition between science and religion.
     An intestine struggle, open or secret, between authority and liberty.   --Hume.
  5. With relation to two, as involved in an act or attribute of which another is the agent or subject; as, to judge between or to choose between courses; to distinguish between you and me; to mediate between nations.
  6. In intermediate relation to, in respect to time, quantity, or degree; as, between nine and ten o'clock.
  Between decks, the space, or in the space, between the decks of a vessel.
  Between ourselves, Between you and me, Between themselves, in confidence; with the understanding that the matter is not to be communicated to others.
  Syn: -- Between, Among.
  Usage: Between etymologically indicates only two; as, a quarrel between two men or two nations; to be between two fires, etc. It is however extended to more than two in expressing a certain relation.
     I . . . hope that between public business, improving studies, and domestic pleasures, neither melancholy nor caprice will find any place for entrance.   --Johnson.
    Among implies a mass or collection of things or persons, and always supposes more than two; as, the prize money was equally divided among the ship's crew.