# Order Types

Orders are instructions to buy or sell assets at specified conditions. They define what, when, and how trades should execute on the exchange. 

Ethereal supports a diverse range of order types and configurations:

* **Market:** Executes immediately against resting liquidity; any unfilled size is canceled.
* **Limit:** Placed at a specific price and stays on the order book until filled or cancelled. Filled at selected limit price or better
  * **GTD (Good-Till-Date):** Stays live until the chosen expiry or when the order fills.
  * **IOC (Immediate-or-Cancel):** Fills what it can instantly, cancels the rest.
  * **FOK (Fill-or-Kill):** Must fill in full at once or cancel entirely.
* **Stop orders**
  * **Stop Market:** A market order that is executed at the best market price when mark price reaches selected market price
  * **Stop Limit:** A limit order that is only executed at selected limit price after mark price reaches selected trigger price.
* **Market close orders:** Automatically-size to fully close your current position, canceling any resting or untriggered orders before closing automatically.
* **Reduce-only orders:** Ensures the order can only decrease your current open position size.
  * **Limit**: Limit reduce-only orders automatically adjust if a subsequent order reduces your current position
* **Trigger orders (OTO / OCO groups):**
  * **OTO (One-Triggers-Other):** First order fills first; then linked order activates once first has concluded.
  * **OCO (One-Cancels-Other):** Linked orders live together. Filling one cancels the others.