In trading on Monday, shares of the First Trust United Kingdom AlphaDEX Fund ETF ( FKU) entered into oversold territory, changing hands as low as $39.48 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of First Trust United Kingdom AlphaDEX Fund, the RSI reading has hit 27.9 — by comparison, the RSI reading for the S&P 500 is currently 57.5. A bullish investor could look at FKU's 27.9 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side. Looking at a chart of one year performance (below), FKU's low point in its 52 week range is $37.80 per share, with $46.11 as the 52 week high point — that compares with a last trade of $39.56. First Trust United Kingdom AlphaDEX Fund shares are currently trading down about 2.5% on the day.