The Tenkan-Sen is a key component of the Ichimoku Kinko Hyo trading system, used in technical analysis to identify trends in financial markets. It is calculated by averaging the highest high and the lowest low over the last nine periods. This line helps traders determine potential support and resistance levels. In practice, the Tenkan-Sen is often used in conjunction with other indicators from the Ichimoku system, such as the Kijun-Sen and Senkou Span. When the Tenkan-Sen crosses above the Kijun-Sen, it may signal a bullish trend, while a cross below can indicate a bearish trend.