/ˈʌndər ˈeɪdʒ/ – Phrase
Definition: vị thành niên.
A more throughout explanation: “Under age” refers to being below the legally established age of majority, which is the age at which a person is considered an adult and is granted full legal rights and responsibilities. This term is often used to describe individuals who are not yet old enough to engage in certain activities or make certain decisions without parental or guardian consent.
Example: The legal drinking age in this country is 21, so it is illegal for anyone under age to purchase or consume alcohol.