A measure of volatility introduced by Welles Wilder in his book: New Concepts in Technical Trading Systems.

The true range indicator is the greatest of the following:
-current high less the current low.
-the absolute value of the current high less the previous close.
-the absolute value of the current low less the previous close.

The average true range is a moving average (generally 14-days) of the true ranges.

|||Wilder originally developed the ATR for commodities but the indicator can also be used for stocks and indexes. Simply put, a stock experiencing a high level of volatility will have a higher ATR, and a low volatility stock will have a lower ATR.