Financial terms, explained from first principles.

Position-closure rule requiring the oldest opened lots to close first. US FX brokers are FIFO-mandated by NFA.

Order time-in-force: expires at session close. Default for intraday-only orders.

Order time-in-force: stays active until filled or manually cancelled. Default for swing-trade limit orders.

Limit order that doesn't display in the public book at all. Sits invisibly waiting for an aggressive market order to find it.

Large order split into smaller visible chunks. Shows a small piece in the book; replenishes when the visible piece fills.

Market-maker right to reject an aggressor order at the quoted price within milliseconds of submission. Asymmetric: accepts when market moves in MM's favor, rejects when it moves against.

Order to buy at a maximum price (or sell at a minimum). Fills only at the limit price or better. Trades price certainty for execution certainty.

Closing an open position via an opposing trade. The standard way out of any leveraged position.

Broker warning that account equity has fallen toward margin requirement. If equity reaches the auto-liquidation threshold, the broker force-closes positions.

Order to buy or sell immediately at the best available price. Fills fastest but exposed to slippage in fast markets.

Pair of orders where filling one automatically cancels the other. Standard wrapper for take-profit + stop-loss on a single position.

Order fills for less than the requested size because counterparty volume at your price is limited. Remainder stays open or cancels.

Broker rejection of an order at the requested price followed by a new offered price. Common on market-maker brokers in fast markets.

Difference between the intended execution price and the actual fill price. Largest hidden cost beyond the spread.

Order that becomes a market order once a trigger price is hit. Used for stop-loss exits and breakout entries.

Brief price move that triggers a cluster of resting stop orders then immediately reverses. Done deliberately by liquidity providers or by emergent algorithmic herd behavior.

Limit order at a planned profit target. Used as the upper bracket in OCO exits.

Stop-loss that dynamically follows price in the profit direction, locking in gains while leaving room for normal pullback.