A formal declaration by a party in reply to a prior declaration by an opponent.
Before a lawsuit goes to trial, each party makes a series of formal written declarations to the court. These declarations are called pleadings. Generally, they consist of factual claims, allegations, and legal defenses; the parties assert their respective versions of what happened and how they want the court to rule. Typically, this involves the plaintiff filing a complaint and the defendant responding with an answer. This process can occur several times, depending on the complexity of the case. For example, a party may amend its pleadings, which in turn allows the opposing party to answer the amended pleading. When the answers respond to the factual assertions of an opponent's prior pleading, for example, by denying them, they are called responsive pleadings. This process is also known as joining issue.
The distinguishing feature of a responsive pleading is that it replies to the merits of the allegations raised by an opposing party. By contrast, parties may choose to ignore the substance of an opponent's pleading and ask the court to dismiss the lawsuit on some other grounds, such as the court's lack of jurisdiction over the suit.