The Collaborative International Dictionary of English v.0.48:

Then \Then\ ([th][e^]n), adv. [Originally the same word as than.
   See Than.]
   1. At that time (referring to a time specified, either past
      or future).
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            And the Canaanite was then in the land. --Gen. xii.
                                                  6.
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            Now I know in part; but then shall I know even as
            also I am known.                      --1 Cor. xiii.
                                                  12.
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   2. Soon afterward, or immediately; next; afterward.
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            First be reconciled to thy brother, and then come
            and offer thy gift.                   --Matt. v. 24.
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   3. At another time; later; again.
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            One while the master is not aware of what is done,
            and then in other cases it may fall out to be own
            act.                                  --L'Estrange.
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   By then.
      (a) By that time.
      (b) By the time that. [Obs.]
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                But that opinion, I trust, by then this
                following argument hath been well read, will be
                left for one of the mysteries of an indulgent
                Antichrist.                       --Milton.
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   Now and then. See under Now, adv.

   Till then, until that time; until the time mentioned.
      --Milton.
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   Note: Then is often used elliptically, like an adjective, for
         then existing; as, the then administration.
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