Diversification is an investment strategy that spreads risk by allocating capital across different assets, sectors, geographic regions, or time periods. The principle behind diversification is that different investments respond differently to market conditions, reducing overall portfolio volatility while maintaining return potential. Proper diversification can significantly improve risk-adjusted returns.

Effective diversification requires understanding correlation relationships between different assets and ensuring that portfolio components don’t all move in the same direction during market stress. Modern portfolio theory provides mathematical frameworks for optimal diversification. However, during extreme market events, correlations may increase, reducing diversification benefits when they’re needed most.

Real-world example: An investor diversifies a $100,000 portfolio across 40% stocks, 30% bonds, 20% commodities, and 10% real estate, reducing overall volatility compared to holding only stocks.