There are many different synonyms for the term "portfolio theory." For example, it could be referred to as "portfolio management theory," "investment theory," or "asset allocation theory." Other possible synonyms might include "risk management theory," "portfolio diversification theory," or "modern portfolio theory." Ultimately, all of these terms refer to the same basic concept: the idea that by investing in a variety of different assets, it is possible to reduce risk and maximize returns over the long term. Whether you are a seasoned investor or just starting out, understanding portfolio theory is an important step in building a successful investment strategy.