Break of Structure (BOS)

A break of structure (BOS) happens when price moves past a swing high or swing low that had been holding a trend's shape together — the level that defined the last leg of a sequence of higher highs and higher lows (or lower lows and lower highs). It's a structural observation: a specific point that mattered got taken out. On its own, it doesn't say what happens next.

How it's usually distinguished from a "shift"

Different educators draw this line slightly differently, but the common distinction is: a market structure shift is the broader idea that the prevailing sequence may be turning, while a break of structure is the specific, confirmable event — price closing beyond a named swing point — that traders point to as evidence of it. Some traders further split out a "change of character" (CHoCH) as the first break against the prevailing trend, reserving "BOS" for a break that continues the trend already in place. Treat the exact labels as convention, not law — different sources use them inconsistently, which is part of why a plain definition is worth having.

Why it's watched, not traded blindly

A break of structure tells you a level that mattered stopped holding — it doesn't tell you why, or whether the move sticks. The same break on a thin, low-participation session reads very differently from the same break on a heavy, news-driven one. It's one input into a broader read of the session, not a standalone trigger.