Glossary
Defendant
The person, business, or entity being sued in a civil case or charged with a crime in a criminal case. The defendant didn't choose to be in court: the plaintiff (or in criminal cases, the government) brought them there.
In a civil case, the defendant is the party the plaintiff has accused of doing something wrong: breaching a contract, causing harm, owing money, etc. The defendant's job is to respond to the accusations, raise defenses, and (if the case goes that far) make their case to the court.
In a criminal case, the defendant is the person accused of breaking a criminal law. The government is the other side, and the defendant has constitutional protections like the right to a lawyer, the right to remain silent, and the right to a jury trial.
In family law, probate, and some appeals, the defendant is sometimes called a respondent instead.