A set of securities that shares a common feature such as the same market capitalization, industry or index. Universe of securities can also refer to securities within a defined price range, securities that deal in specific commodities and/or securities with the same product line.
A universe of securities is usually referred to in the context of technical analysis to backtest for technical trading strategies. For example, in order for a technical trader to test a specific trading strategy targeted toward small-cap stocks, he or she will need to limit backtesting analysis to include only small caps. Thus, a trading strategy geared toward a specific universe of securities may not provide reliable results if the strategy is tested on a broad universe of securities.