Webster's Revised Unabridged Dictionary · 1913

Then

Then (ten) , adverb

[Originally the same word as than. See Than.]

1.
At that time (referring to a time specified, either past or future).
And the Canaanite was then in the land. — Gen. xii. 6
Now I know in part; but then shall I know even as also I am known. — 1 Cor. xiii. 12
2.
Soon afterward, or immediately; next; afterward.
First be reconciled to thy brother, and then come and offer thy gift. — Matt. v. 24
3.
At another time; later; again.
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
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
Collocations (3)
By then , (a) By that time. (b) By the time that. [Obsolete]
Now and then , See under Now, adv.
Till then , until that time; until the time mentioned. — Milton

Then is often used elliptically, like an adjective, for then existing; as, the then administration.

Then , conjunction

1.
Than. [Obsolete] — Spenser
2.
In that case; in consequence; as a consequence; therefore; for this reason.
If all this be so, then man has a natural freedom. — Locke
Now, then, be all thy weighty cares away. — Dryden