Trend lines are straight lines drawn on charts connecting successive price peaks (resistance trend lines) or troughs (support trend lines) to visualize trend direction and potential support or resistance levels. These lines help identify trend channels, breakout points, and potential reversal signals in technical analysis.

Trend line validity increases with more touch points and duration, while breaks often signal trend changes or acceleration. Different trend line types include ascending, descending, and horizontal lines that provide various analytical insights. Understanding trend line construction and interpretation helps improve technical analysis accuracy.

Real-world example: EUR/USD forms an ascending trend line connecting lows at 1.1000, 1.1050, and 1.1100 over three months, providing support for long positions until a break below the line signals potential trend reversal.