The ADX measures the strength of a prevailing trend as well as whether movement exists in the market. A low ADX value (generally less than 20) can indicate a non-trending market with low volatility whereas a cross above 20 may indicate the start of a trend (either up or down). If the ADX is over 40 and begins to fall, it can indicate the slowdown of a current trend. This indicator can also be used to identify non-trending markets, or a deterioration of an ongoing trend. Although market direction is important in its calculation, the ADX is not a directional indicator.
Length(14) sets the number of bars to use in the calculation of ADX.