A gap — where price opens well away from the prior close — isn't one thing. There are four types, and telling them apart matters because each implies a different next move.

Common and breakaway

A common gap happens inside a range on no real news — minor, and it usually fills quickly. A breakaway gap occurs when price gaps out of a consolidation or through a key level, on heavy volume — the start of a new trend. Breakaway gaps often don't fill soon, because they mark a genuine shift in control.

Runaway and exhaustion

A runaway (continuation) gap appears mid-trend as a strong move accelerates — a sign of conviction, price leaping in the trend's direction. An exhaustion gap comes near the end of an extended move, often on a volume spike — the last frantic push before reversal. The trap: an exhaustion gap and a runaway gap look similar in the moment; the difference is where you are in the trend and what happens right after.

A breakaway gap starts the move, a runaway gap fuels it, an exhaustion gap ends it. Same gap, three very different futures.

Reading them

Volume and location are the keys: heavy volume breaking a level = breakaway; strong volume mid-trend = runaway; a climactic volume spike after a long run that quickly reverses = exhaustion. Since they resemble each other in real time, gaps are best read alongside volume and structure — and, on SPY, the context of overnight news and dealer positioning.