Underlying asset

The underlying asset is the financial instrument that an options contract derives its value from. For equity options, the underlying is 100 shares of a specific stock or ETF. The price of the underlying is the primary driver of an option's intrinsic value and delta.

Common underlyings for options trading:

• Individual stocks: AAPL, TSLA, NVDA, MSFT, AMZN
• Broad market ETFs: SPY (S&P 500), QQQ (Nasdaq 100), IWM (Russell 2000)
• Sector ETFs: XLF (financials), XLE (energy), XLK (technology)
• Index options: SPX, NDX (cash-settled, European-style)

Why the underlying matters: Different underlyings have fundamentally different volatility profiles, liquidity, and behavior. Liquid underlyings (SPY, QQQ, large-cap stocks) have tight bid-ask spreads and deep options chains. Illiquid underlyings can make trading difficult and expensive regardless of your options strategy.

Understanding contract size: One standard US equity options contract controls 100 shares of the underlying. All premium quotes, Greeks, and P&L calculations are per share , multiply by 100 for the actual dollar impact.

Cash-settled vs share-settled: Most equity options are share-settled , exercise results in an actual stock transaction. Index options like SPX are cash-settled , no shares change hands; the difference between the index level and the strike is paid in cash.

Example: You buy a call on AAPL. The underlying is AAPL stock. If AAPL rises $5, your call gains approximately delta × $5 × 100. Every move in AAPL's stock price directly drives your option's value.

Related terms: Delta, premium, strike price, call option, put option, liquidity

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