Definition
Gain or loss relative to the amount invested, usually expressed as a percentage. The period and treatment of costs matter.
Hypothetical example
Buy at 100, sell at 120 and pay total fees of 2: net gain is 18 and simple return is 18%.
Keep in mind
Cumulative and annualized returns differ. Deposits and withdrawals make account performance more complex than a simple price comparison.
Official reference
www.investor.gov ↗Examples are illustrative assumptions, not investment recommendations.