Which of the following best defines a juvenile?

The definition of a juvenile typically refers to a legal standard for individuals who have not yet reached the age of majority, which is commonly set at 18 years old in many jurisdictions. In this context, the term "juvenile" identifies someone who is still considered a minor and is therefore subject to different laws, protections, and processes than adults.

Choosing an age threshold of 18 aligns with the legal definition used in many statutes, including those related to juvenile justice and family law. Individuals under 18 are generally treated differently in legal situations, such as court proceedings or criminal justice matters, recognizing their developmental differences compared to adults.

The other options do not align with this standard definition. For example, setting the age at 20 would encompass some individuals who are legally adults, while stating that a juvenile can be a married individual or someone in the military introduces criteria unrelated to age alone. Thus, under most legal frameworks, the best definition of a juvenile is indeed someone under 18 years old.