Summary
ADX, or Average Directional Index, describes the strength of a trend without defining its direction on its own.
Parameter
Period controls the number of observations used to smooth the directional movement calculation. The default is 14. A shorter period reacts faster but can be more variable; a longer period is smoother and slower.
How to read it
Review the ADX value together with the directional components and the underlying price chart. A stronger reading can indicate a more established trend, while a weaker reading can describe less directional movement.
Things to keep in mind
ADX is a lagging, historical measure. It does not by itself show whether prices should rise or fall.