In plain English
What Partial fill means
An order may be too large for the available liquidity at one price, or market conditions may change before the whole order can be matched. In that case, the venue fills part of the order and leaves the rest open, canceled, or waiting depending on the order type.
Why it matters
Partial fills matter because they change average execution price, timing, and whether the trader still has exposure to complete the remaining quantity. They are common in less liquid markets, larger orders, and fast markets where available size at each price level is limited.
Example
A trader enters a limit order to buy 10 lots. The market only offers 4 lots at the limit price, so 4 lots are filled and 6 remain working. The order has a partial fill. This simplified example assumes a single price level.
Quick answers
Common questions
Can a market order get a partial fill?+
Yes. If there is not enough opposite-side liquidity available immediately, the order may be filled in pieces at different prices.
Does a partial fill always mean the rest will execute later?+
No. The remainder may later fill, stay open, or be canceled, depending on the order type and venue handling.
Sources