then 
(thĕn)
(thĕn)adv.
1. At that time: I was still in school then. Come at noon; I'll be ready then.
2. Next in time, space, or order; immediately afterward: watched the late movie and then went to bed.
3. In addition; moreover; besides: It costs $20, and then there's the sales tax to pay.
4. Used after but to qualify or balance a preceding statement: The star was nervous, but then who isn't on the first night of a new play.
5. In that case; accordingly: If traffic is heavy, then allow extra time.
6. As a consequence; therefore: The case, then, is closed.
conj.
Usage Problem And after that: I showered, then combed my hair.
n.
That time or moment: The bus leaves at four; until then let's walk.
adj.
Idiom: Being so at that time: the then chairman of the board.
then again
From another standpoint; on the other hand: I need a vacation. Then again, so do my coworkers.
[Middle English, from Old English thenne; see to- in the Appendix of Indo-European roots.]
Usage Note: Sticklers for grammar sometimes assert that then is not a coordinating conjunction, and that the sentence She took a slice of pie, then left is thus incorrect; it must be rewritten as She took a slice of pie and then left, in which the then acts as an adverb and the halves of the compound predicate are linked by the coordinating conjunction and. But this use of then as a coordinating conjunction is actually both widespread and widely accepted; in our 2012 survey, more than three quarters of the Usage Panel found the sentence She took a slice of pie, then left completely acceptable. Note, though, that the punctuation of this conjunctive use of then differs from the usual punctuation for similar sentences using and. No comma is needed when and links the parts of a compound predicate, as in She took a slice of pie and left. When then joins the halves of the predicate, a comma is usually required; only 8 percent of the Panel approved of She took a slice of pie then left.