Some people—mostly journalists, but even some lawyers—refer to all court papers as “pleadings.” In precise usage, however, pleadings are the documents containing the written allegations that each party must communicate to the opponent before trial so that each will know what contentions must be supported (or rebutted) by the evidence. Examples are complaints, petitions (in some jurisdictions), answers, counterclaims, and cross-claims. Among the many court papers that aren’t pleadings are motions, briefs, affidavits, and discovery requests.
In federal court, a complaint begins a lawsuit, describes the harm suffered by the plaintiff, identifies the party responsible and how that party caused the harm, and requests a remedy. The complaint must state facts that, if proved, would entitle the plaintiff to relief. The defendant must then admit or deny each of the plaintiff’s allegations and may also raise defenses and assert compulsory counterclaims. A defendant who can’t admit or deny an allegation for lack of information customarily disclaims knowledge of its truth or accuracy.
One key to good pleading is to keep statements as simple and concise as practical, even when a rule requires you to plead with particularity. Use idiomatic English: unless a rule requires technical expressions or particular forms of words, use plain language that best states the claims or defenses.
Good pleadings have two practical advantages. First, they often require the adversary to stake positions exactly and clearly, often on issues that the adversary would prefer not to have exposed. Second, they often lead to settlements: if you can make your case look especially strong on the pleadings, the other side may decide not to risk a full-blown trial.
Garner’s Dictionary of Legal Usage 682–83 (3d ed. 2011).
The Redbook: A Manual on Legal Style 473–80 (4th ed. 2018).