Dash: Marking Sharp Turns In Thought, Restatements, Amplifications
Dashes can act like little warnings (like yellow road signs) that whatever the writer has been doing is about to change. Dashes identify a sudden break in the sentence as the writer changes tack, perhaps going entirely in another direction, or perhaps just pausing to insert another thought. This effect is usually fairly informal, and isn’t recommended for academic writing (as it might look like you don’t know what you’re talking about).
Mary, could you – no, Mikey, don’t touch the sharp knife! – Mary, could you please set the table?
A “sharp turn in thought” could be the switch when suddenly talking to a new person.
Dinner is at 6:30 – not 6:29 or 6:31.
This dash is for emphasis on the “amplification”: making sure the time is clarified.
Where the heck is my – wait, what was I looking for?
Would you please – oh, never mind….