A more thorough explanation:

Mutua petitio is a Latin term used in Scots law to refer to a counterclaim made by a defendant against a plaintiff. It is also known as a counterclaim.

For example, if a plaintiff sues a defendant for breach of contract, the defendant may file a mutua petitio or counterclaim against the plaintiff for breach of the same contract. Another example is if a plaintiff sues a defendant for damages caused by a car accident, the defendant may file a mutua petitio or counterclaim against the plaintiff for damages caused by the same accident.

These examples illustrate how mutua petitio or counterclaim allows the defendant to assert their own claims against the plaintiff in the same lawsuit. It helps to avoid multiple lawsuits and promotes efficiency in the legal process.