Delta
Also called Δ, option delta
How much an option's price changes for a $1 move in the underlying, and roughly how many shares it behaves like.
Delta is how much an option's price moves for a $1 move in the underlying. A call with a delta of 0.30 gains about 30 cents when the stock rises a dollar. Calls have delta from 0 to 1, puts from 0 to −1.
Delta also reads as a share equivalent: one contract of a 0.30 delta call behaves like about 30 shares. That's why a dealer short that call buys about 30 shares to hedge it.
Traders often use |delta| as a rough chance the option finishes in the money: a 0.15 delta put is sometimes read as about a 15% chance. It's an approximation that leans on the option's own implied volatility.
What changes delta
In Theta Vantage
The option chain shows each contract's delta (Δ). The strike selector ranks strikes by how close they sit to your target delta, and wheel and income can pick strikes by it. Dealer delta (DEX) adds delta up across the chain from the dealer's side.