S&P 500
A market-cap-weighted index of 500 large US companies. The most widely used benchmark for US stock market performance.
The S&P 500 is maintained by S&P Dow Jones Indices and tracks 500 large-cap US-listed companies selected by a committee based on market cap, liquidity, profitability, and other factors. Its full name is the Standard & Poor's 500.
Being market-cap weighted means the largest companies — Apple, Microsoft, Nvidia — have the most influence on the index level. The top 10 holdings can represent 30%+ of the index, creating concentration risk.
The S&P 500 is the professional benchmark: fund managers are measured against it, retirement accounts default to S&P 500 index funds, and options on the index (SPX) are among the most liquid instruments in the world.
Related Terms
Beta
A measure of a stock's volatility relative to the market. Beta > 1 means it moves more than the index; Beta < 1 means it moves less.
IntermediateBlue-Chip Stock
Shares of a large, well-established company with a long track record of stable earnings and often consistent dividends.
BeginnerCircuit Breaker (Market-Wide)
An exchange-wide trading halt triggered by a sharp S&P 500 drop, pausing all US stock trading to curb panic selling.
AdvancedDow Jones Industrial Average
A price-weighted index of 30 major US blue-chip companies. The oldest US stock index, widely covered in media but less representative than the S&P 500.
BeginnerETF
A basket of securities that trades on an exchange like a single stock. ETFs give instant diversified exposure to an index, sector, or theme.
BeginnerLarge Cap
Companies with a market capitalization generally above $10 billion. Large caps are the most liquid, most-analyzed tier of the stock market.
BeginnerNasdaq Composite
A market-cap-weighted index of all ~3,000+ companies listed on the Nasdaq exchange, with heavy weighting toward technology.
BeginnerRelative Strength (vs Index)
How a stock or sector is performing compared to a benchmark index like the S&P 500. Outperforming the index = positive relative strength.
IntermediateSector
A broad grouping of companies with similar business activities. The S&P 500 uses 11 GICS sectors such as Technology, Financials, and Energy.
Beginner