A more thorough explanation:

Definition: Debet et detinet is a legal term that means "he owes and detains." It was used in declarations in actions for debt when the original creditor sued the original debtor. The declaration stated that the defendant "owes to" as well as "detains from" the plaintiff the debt or thing in question.

• John borrowed $100 from Jane and has not paid her back. Jane can sue John for the debt he owes and the fact that he is detaining her money. This is known as an action in debet et detinet.
• If John had died and his executor refused to pay Jane back, she could still sue for the debt alone. This is known as an action in detinet alone.

The examples illustrate how debet et detinet was used in legal actions for debt. It was used to describe the situation where the debtor owed money and was also detaining the creditor's property or money. If the action was brought against someone other than the original debtor, then the action was said to be "in the detinet alone."