then: at that time, or as the next thing that happens
This little word answers the question "when?" with the answer "then." It does that in two closely related ways. Most often it links one event to the one just before it, meaning roughly "after that" or "next": it is the hinge a storyteller uses to move from one scene to the next. Less often it points to a particular moment in time, whether a past time the writer is recalling or a future time still to come, and means "at that time."
The two uses are the same idea seen from two angles. Pointing to "that time" and marking "the next thing" both fix an event at a spot on a timeline; the difference is only whether the writer is chaining events together or singling out a moment. Both are carried comfortably by the English word "then," which has the very same double life.
Matthew leans on this word more than any other writer in the New Testament, using it again and again to stitch his account together, so that "then Jesus," "then Herod," "then the disciples" becomes the steady drumbeat of his Gospel. In teaching about the last days it takes on weight, marking the decisive future moment when a long-awaited thing finally happens: "then the Son of Man will appear," "then they will see."