In trading on Thursday, shares of the First Trust Senior Loan Fund ETF ( FTSL) entered into oversold territory, changing hands as low as $48.05 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 Senior Loan Fund, the RSI reading has hit 27.3 — by comparison, the RSI reading for the S&P 500 is currently 59.2. A bullish investor could look at FTSL's 27.3 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), FTSL's low point in its 52 week range is $46.18 per share, with $48.63 as the 52 week high point — that compares with a last trade of $48.07. First Trust Senior Loan Fund shares are currently trading down about 0.3% on the day.