Partially means incompletely or only to some degree. When something is done partially, it's started but not finished, or it's true in some ways but not others.

If you partially clean your room, you might make your bed and pick up clothes but leave books scattered everywhere. If a window is partially open, there's a gap letting in fresh air, but it's not wide open. When a puzzle is partially complete, you've connected many pieces but haven't filled in the whole picture yet.

The word helps us describe things that exist in a middle state, neither fully one way nor the other. A partially cloudy sky has both clouds and sunshine. A student who partially understands a math concept grasps some parts but still feels confused about others.

You might say “I'm partially responsible for the mess” if you contributed to it but weren't the only one involved. The opposite would be fully, completely, or entirely.