An order turns an idea into instructions: buy or sell, how much, at what price, and under which conditions. The first choice is whether to trade against someone else's available price or leave a price for someone else to accept.
Taking a quote buys immediacy and crosses the spread. Leaving a resting limit order can improve the entry price, but introduces uncertainty about whether it fills and what the market will look like when it does. Neither is automatically the better trade.
Market and limit orders
A market order attempts immediate execution against available orders. A buy takes offers; a sell takes bids. If the quantity exceeds what is available at the best price, the remaining amount can fill at worse levels. The price of the last trade on the chart is not a promise about your average fill.
A limit order sets the worst price you will accept. A buy limit at $100 can execute at $100 or below. A sell limit at $100 can execute at $100 or above. The boundary controls price, but does not guarantee a fill. The SEC's order guide explains this distinction.
A limit order can still cross the spread. If the best ask is $99.90, a buy limit at $100 can execute immediately against it. “Limit” describes the price constraint; “maker” and “taker” describe whether the order rests or consumes existing liquidity. A post-only instruction prevents immediate taking, subject to the venue's rejection or cancellation rules.
The hidden tradeoff in a resting order
Return to a $99.995 bid and $100.005 ask. Buying immediately pays the ask. Joining the bid could save $0.01 per unit compared with that purchase, if the order fills and the later market path is otherwise the same.
The condition matters. Suppose bad news makes the market worth about $99.80 before your resting bid is canceled. Someone can sell to your $99.995 bid. You obtained the price you requested, but that price is now about $0.195 above the new value. This is adverse selection: the circumstances making another trader willing to fill your order can also make the fill unfavorable for you.
The reverse problem is missing a good trade. If the market rises without touching your bid, saving the spread was never an available outcome. A temporary seller could also fill your order before the price recovers, giving a favorable result. A resting order's value depends on the mix of those paths. The SEC's execution research discusses this selection problem.
Match the instruction to the idea. An opportunity that disappears quickly may justify paying for immediacy. A slow valuation view may tolerate waiting at a chosen price. Evaluate the missed trades as well as the filled ones; comparing only successful limit fills with all market fills gives an incomplete picture.
What makes you exit
A position should have conditions under which you reduce or close it. That can be a price that invalidates the setup, evidence contradicting the thesis, a target being reached, or the expected event failing to arrive. An exit turns an open-ended exposure into a decision you can review.
For our 20-unit long from $100, an intended exit at $97 implies a $60 gross loss if it fills exactly. This is useful for sizing, but the order type determines what happens when $97 is no longer available.
| Instruction | What it does | Main uncertainty |
|---|---|---|
| Stop-market | Triggers a market order | Execution price after the trigger |
| Stop-limit | Triggers an order with a price limit | Whether the order fills |
| Take-profit limit | Closes at a chosen favorable price or better | Whether that price trades in enough size |
| Trailing stop | Adjusts a trigger after favorable movement | Whether ordinary fluctuations trigger an exit |
A sell stop-market triggered at $97 could fill at $96.40 after a gap, producing a $72 gross loss. A stop-limit with the same trigger and a $96.90 sell limit cannot execute below $96.90. It may leave the position open while bids sit at $96.40. A price boundary and a guaranteed exit are different objectives.
Orders after the position changes
Check which price activates the trigger: the last trade, mark price, or another specified measure. Also read the order's duration. A good-til-canceled instruction can outlive the original idea; immediate-or-cancel removes any quantity that cannot execute in its immediate attempt. Hyperliquid's documentation describes its supported instructions.
If you place a sell exit for 20 units, then manually sell eight, only 12 remain. An unrestricted sell for the original 20 could close those 12 and open an eight-unit short. A suitable reduce-only instruction constrains the order to reducing an existing position. After partial fills or manual changes, read both the position and the outstanding orders.
The same applies to a take-profit and stop working together. Automatic cancellation requires the appropriate linkage; verify the remaining order's status when one fills. Practicing an entry, partial exit, final close, and cancellation in a simulation teaches the operating sequence before you need it in a moving market.
Choose the instruction: You only want to buy at $100 or below, but the best offer is $100.20. Which order preserves your price condition, and what do you give up?
Show the answer
A buy limit at $100 preserves the boundary. You accept the possibility of no fill. A market order could buy immediately above $100; a later fill at your limit could also occur after the outlook deteriorates.