denk

In a sentence

• Ich denke, du bist müde.

  I think you are tired.

  In this sentence, "denke" is used to indicate the act of thinking, opinion forming.

• Denk daran, die Tür zu schließen.

  Remember to close the door.

  Here, "denk" is used as an imperative form of the verb, used to instruct someone to remember or think about something.

• Er sagt, dass er nicht klar denken kann.

  He says that he cannot think clearly.

  In this context, "denken" is used to mean the process of reasoning or mental activity.