What does it mean if my order is “partially filled?”

A partially filled order means that only part of your order was matched.

Example:
If you tried to buy 100 shares but only 40 shares were available at your price, you’ll get 40 shares first. The remaining 60 shares will stay open until they are matched, cancelled, or expire.

This happens because stocks are traded between many investors, and available quantities can change throughout the day.