If you want the dictionary definition, just double click on any word.

The verb - When you concentrate you direct all your efforts towards a particular activity, subject or problem.

For example: You need to concentrate harder when you listen to something in another language.

The adjective - If something is concentrated it means it has had some liquid removed.

For example: I prefer freshly squeezed orange juice to concentrated.

!Note The simple past of "to concentrate" is "concentrated" this is where the confusion may arise.

For example: She concentrated very hard in the exam.