Which term describes a brief comment or explanation found in legal sources?

The term that best describes a brief comment or explanation found in legal sources is "annotation." Annotations provide additional insights, interpretations, or explanations regarding the law, legal cases, statutes, or regulations. They serve as a valuable resource for legal professionals, allowing them to understand complex legal concepts, highlight significant points, and clarify case law.

Annotations are commonly found in legal textbooks, case law compilations, and legal research databases, where they accompany statutes or case summaries to provide context and meaning. This helps practitioners and students navigate and comprehend the intricacies of legal texts.

In contrast, the other terms do not fit the description provided in the question. "Amicus curiae" refers to a person or organization that offers information to a court on a matter affecting a case, but it does not imply a brief explanation within a legal source. "Appeal" is the process of seeking a higher court's review of a decision made by a lower court, while "defendant's statement" generally refers to the explanation or commentary made by the defendant in a legal case, which also does not align with the concept of a brief comment in legal literature.