Basics

Index

By Ryan Silk & Lawrence Polatchek · Reviewed April 2026 · Options Trading Glossary

Statistical measure of grouped asset performance

What is Index?

Index A statistical measure tracking the performance of a group of assets. Major indices include the S&P 500, Nasdaq 100, and Russell 2000. Index options (like SPX) are cash-settled and European-style, while ETF options (like SPY) are physically settled and American-style.

Complete Definition

A statistical measure tracking the performance of a group of assets. Major indices include the S&P 500, Nasdaq 100, and Russell 2000. Index options (like SPX) are cash-settled and European-style, while ETF options (like SPY) are physically settled and American-style.

Example

The S&P 500 index tracks 500 large-cap US stocks. SPX options settle in cash, while SPY ETF options deliver shares.

Related Terms

Etf European Option Vix Index

Written by

ApexVol Research Team

Quantitative options research

All calculations use live ORATS institutional data — the same source used by professional volatility desks.

Technical reviewer

Ryan Silk, ApexVol Founder

Reviewed for technical accuracy

10+ years trading options. Built ApexVol's pricing engine, Greeks model, and IV-rank methodology.

This guide is updated as market conditions and ORATS data change. Last revised 2026-05-12. How we research →

Want to Learn More?

Explore our educational resources and analytics tools to deepen your understanding.

Learning Center

In-The-Money (ITM) All Terms Intrinsic Value

Learn Options Trading

Understanding Options Greeks Implied Volatility Guide How to Trade Options 0DTE Options Trading Options Glossary Strategy Guides Learning Center

Explore More Tools

Options Chain Real-time Greeks Greeks Heatmap Visual analysis Volatility Lab IV analysis Strategy Simulator Test strategies IV Intelligence 3D visualization Options Screener Find opportunities Historical Data Past snapshots Earnings Historical moves & IV 0DTE Analytics Same-day expiration