Harmonic Pattern
A family of five-point shapes — Gartley, Bat, Butterfly, Crab — whose legs are required to stand in specific Fibonacci ratios to one another rather than merely to look a certain way.
What separates harmonics from the rest of technical analysis is that the definitions are arithmetic: a Gartley requires its B point near 61.8% of the first leg and its D point near 78.6%, within a tolerance, and a shape that misses those ratios is not a loosely formed Gartley but a different shape. That precision makes them easy to detect reliably and does not, by itself, make them predictive. Whether the ratios carry information is an empirical question, and the answer is the measured record on each pattern's own page.