A gun is a muzzle or breech-loaded projectile-firing weapon. There are various definitions depending on the nation and branch of service. A "gun" may be distinguished from other firearms in being a crew-served weapon such as a howitzer or mortar, as opposed to a small arm like a rifle or pistol, but there are exceptions, such as the U.S. Air Force's GUU5/P. At one time, land-based artillery tubes were called cannon and sea-based naval cannon were called guns. The term "gun" evolved into a generic term for any tube-launched projectile-firing weapon used by sailors, including boarding parties and marines.

In modern parlance, a gun is a projectile weapon using a hollow, tubular barrel with a closed end — the breech — as the means of directing the projectile (as well as other purposes, for example stabilizing the projectile's trajectory, aiming, as an expansion chamber for propellant, etc.), and firing in a generally flat trajectory.

The term "gun" has also taken on a more generic meaning, by which it has come to refer to any one of a number of trigger-initiated, hand-held, and hand-directed implements, especially with an extending bore, which thereby resemble the class of weapon in either form or concept. Examples of this usage include staple gun, nail gun, glue gun, grease gun. Occasionally, this tendency is ironically reversed, such as the case of the American M3 submachine gun which carries the nickname "Grease Gun".

A court is a form of tribunal, often a governmental institution, with the authority to adjudicate legal disputes between parties and carry out the administration of justice in civil, criminal, and administrative matters in accordance with the rule of law. In both common law and civil law legal systems, courts are the central means for dispute resolution, and it is generally understood that all persons have an ability to bring their claims before a court. Similarly, the rights of those accused of a crime include the right to present a defense before a court.

The system of courts that interpret and apply the law are collectively known as the judiciary. The place where a court sits is known as a venue. The room where court proceedings occur is known as a courtroom, and the building as a courthouse; court facilities range from simple and very small facilities in rural communities to large buildings in cities.

The practical authority given to the court is known as its jurisdiction (Latin jus dicere) -- the court's power to decide certain kinds of questions or petitions put to it. According to William Blackstone's Commentaries on the Laws of England, a court is constituted by a minimum of three parties: the actor or plaintiff, who complains of an injury done; the reus or defendant, who is called upon to make satisfaction for it, and the judex or judicial power, which is to examine the truth of the fact, to determine the law arising upon that fact, and, if any injury appears to have been done, to ascertain and by its officers to apply a legal remedy. It is also usual in the superior courts to have attorneys, and advocates or counsel, as assistants, though, often, courts consist of additional attorneys, bailiffs, reporters, and perhaps a jury.