Glossary

Zero days to expiration. An option that expires the same trading day.

Options on the S&P 500 index: cash-settled, European-exercise, listed every trading day.

A call gains value as the underlying rises above the strike; a put gains value as it falls below.

The fixed price at which an option settles.

When the option resolves. For 0DTE SPX, the 4:00 PM ET close.

The instrument an option is based on (here, the SPX index).

Where the strike sits relative to the underlying: in the money (ITM), at the money (ATM), or out of the money (OTM).

The grid of all strikes with their calls and puts.

The best buy price, best sell price, and their midpoint. Market orders fill at the natural price (ask buying, bid selling); the mid is what a resting limit or stop order waits for.

The size of the move the option market implies for the underlying by expiration, derived from option prices.

What an option would be worth if it expired right now: the amount it is in the money (zero for ATM and OTM options).

The part of an option's price above its intrinsic value; time value that decays to zero by expiration.

Sensitivity to a $1 move in the underlying (decimal 0–1; signed by position direction).

The rate of change of delta.

Time decay per day (negative for long options, positive for short).

Sensitivity to a 1% change in implied volatility.

The market's expected volatility, as an annualized decimal (0.142 = 14.2%).

A model price derived from the Greeks, used when no live quote is available.

One instrument within an order. Multi-leg orders combine several.

Fill now at the natural price / fill once the market holds at your chosen price for three seconds, at that price — or, if you priced past the market, at once and at the market you crossed / trigger at a price, then fill at the market.

Cash out (net buying) / cash in (net selling).

A spread, condor, or other structure submitted and filled atomically.

Two options of the same type and expiration at different strikes, one bought and one sold; both risk and profit are capped.

A four-leg structure selling an OTM call spread and an OTM put spread; profits if the underlying stays between the short strikes.

A holding aggregated by instrument and direction, with live P&L and Greeks.

The sum of delta across all positions; your directional exposure.

A plot of profit/loss versus the underlying price for your positions.

Locked-in gain/loss from closed positions and settlement / mark-to-market on open positions.

opening balance + the day's total P&L.

Available capital after margin is reserved against short positions.

Capital reserved against open shorts, per FINRA-style rules.

Per-leg brokerage charges applied to every order.

A per-account execution-drag setting (a multiple of $0.05) that makes limit and stop orders harder to fill — the market has to move that much further past your price — and worsens every fill that prints at the market, though never past the natural price. Applied identically in practice, live trading, and backtests (as a flat per-contract cost at read time for backtests).

End-of-day resolution of open options at the 4:00 PM ET close.

A persistent, cash-only trading container with a continuous balance that carries day to day, used for live trading and by bots (broker engines coming soon). Replaying past days doesn’t use an account — see Practice.

The account-less sandbox for past trading days: each day is a one-click, fixed $100,000 session with full control of the clock.

The read-only review of a live account's settled day: scrub the clock through the day you actually traded.

One trading day: a chosen past date (practice, account-less) or today under a live account. Orders, positions, transactions, and the equity curve all live under a session.

An account's settled carry; the cash that has rolled day to day. It never folds in an in-progress day's unrealized P&L.

A reusable, testable definition of entries and exits, made with the builder. Immutable once saved; clone it to iterate.

A replay of a strategy across the full history with performance metrics.

A named collection of saved strategies whose results are aggregated at read time, each member an equal $100k sleeve.

A dedicated account that runs a saved strategy hands-free against the live session, with a risk policy and automatic order re-pricing.

Visitors can watch the most recent session; a free account unlocks everything.