General (not jurisdiction-specific)

A person licensed by a state’s highest court or bar to practice law and represent others in legal matters — a lawyer. The title “Esq.” is a courtesy, not a license. Compare attorney-in-fact, an agent under a power of attorney.

An agent authorized to act for another person under a power of attorney. An attorney-in-fact does not need to be a lawyer and cannot practice law for the principal unless licensed; the agent owes the principal duties such as acting in good faith and within the scope of the authority granted.

A written document in which one person (the principal) authorizes another (the agent, or attorney-in-fact) to act on the principal’s behalf in legal or financial matters. A durable power of attorney remains effective if the principal becomes incapacitated. Under the Uniform Power of Attorney Act, adopted in many states, a power of attorney is durable unless it expressly provides otherwise (UPOAA § 104).

A person appointed by a court with the legal authority and duty to care for another person, called a ward — such as a minor or an adult who cannot manage his or her own affairs — or the ward’s property. A guardian ad litem is appointed to protect the interests of a minor or incompetent person in a particular lawsuit (Fed. R. Civ. P. 17(c)(2)).

A person under the age of majority, which is 18 in most states; a few states set it higher. Minors generally may disaffirm most contracts, and in federal court a minor sues or defends through a general guardian, a next friend or a guardian ad litem (Fed. R. Civ. P. 17(c)).

A person or organization that engages a lawyer for legal services. A lawyer owes a client duties of competence, communication, confidentiality and loyalty under the state’s rules of professional conduct, and confidential lawyer-client communications made to obtain legal advice are generally protected by the attorney-client privilege.

A written legal argument submitted to a court. Appellate briefs follow detailed rules on contents, length and format (Fed. R. App. P. 28, 32), and trial courts receive briefs supporting or opposing motions. An amicus curiae brief is filed by a non-party (Fed. R. App. P. 29).

A written statement or note. In motion practice, a memorandum of points and authorities (or memorandum of law) sets out the facts, the law and the argument supporting or opposing a motion. Courts also issue memorandum opinions, and parties may sign a memorandum of understanding.

An introductory statement at the beginning of a constitution, statute or contract that explains its purposes. The Preamble to the U.S. Constitution begins “We the People of the United States”; the Supreme Court has explained that, although it states the Constitution’s general purposes, it “has never been regarded as the source of any substantive power” conferred on the government (Jacobson v. Massachusetts, 197 U.S. 11, 22 (1905)).

Belonging to, or concerning, the people as a whole or the government. For example, public law governs the government and its relationship with individuals, such as constitutional, administrative and criminal law. Similarly, public records are government records that people can inspect under applicable law, and courts presume that court records are open to the public.