A more thorough explanation:

Definition: An informal issue is a point in dispute between two or more parties that arises when a defendant does not properly or fully plead in answer to a material allegation.

Example: In a court case, the plaintiff may make a material allegation against the defendant. If the defendant does not respond to the allegation properly or fully, an informal issue may arise. For example, if the plaintiff alleges that the defendant breached a contract, but the defendant only responds by saying they did not breach the contract without providing any further explanation, an informal issue may arise.

This example illustrates how an informal issue can arise when a defendant does not properly or fully respond to a material allegation made by the plaintiff.