Definition
An All or None Order (AON) is an order that has a set price and is made to purchase or sell a specified volume of assets.
Understanding the Term
An All or None Order (AON) is a common type of structured order with specified steps on how it must be completed. To purchase or sell a volume of assets, the entire size of the order must be filled. Partial fills are unallowed and will not trigger an exchange of any sort.
Takeaway
All or none (AON) is an order type with the instruction to fill the order completely or cancel it; partial fills are not allowed. That is, the price is always set.