In Dow Theory, the major multi-month or multi-year direction of the market, which secondary reactions interrupt but do not end.
Dow described three scales at once: the primary trend lasting a year or more, secondary reactions lasting weeks to months and typically retracing a third to two thirds of the primary move, and minor fluctuations of days that he considered noise.
The framework's discipline is that a secondary reaction, however frightening, does not change the primary trend until the structure of higher-highs-higher-lows actually breaks. This is the direct ancestor of modern market-structure analysis.
The practical caution is scale confusion. Most traders operate on the minor scale Dow dismissed as noise, then borrow primary-trend logic to justify holding losers. Be explicit about which scale a given claim applies to; see multi-timeframe-analysis.
Original diagrams for the ideas on this page. Illustrative, not real market data.
How timeframes stack up. A daily candle is not different data, only coarser data: it opens where the first six-hour candle opened, closes where the last one closed, and its wicks reach the highest and lowest prices any of the four touched.
Educational only, not advice. Spotted an error? Post in Site Feedback.