MinorもUnderageも「未成年者」を指しますが、Underageは飲酒、婚姻などの「法定年齢に満たない者」も意味します。Minorは法律用語です。
国や地域によって成人の年齢が異なります。アメリカは１８−２１歳、カナダは１８−１９歳の間のようです。
Minorとunderageを使って例文を紹介しますね。
Underaged drinking is a serious issue in Japan.
「未成年者の飲酒は日本の深刻な問題です。 」
Minors are not allowed to enter.
「未成年者は入場できません。」
He's under age (for marriage, smoking, drinking etc)
He's too young (to get married). He's still a minor.
Legally, he can't drink in a pub yet.
A 'minor' in England is generally someone under the age of 18.
However, a mnor in terms of criminal rsponsibility is a child under 11 years old.
'Under age' is the favorite expression for any specific scenario.
We wanted to go to a bar but my friend is still under-age for liquor.
In almost every country There are strict rules applied to access to certain
products or services...(and the age varies from 18-21)
You would need "to be of legal age" to buy Alchohol Cigarettes etc...
in Japan anyone who is under 20 years old is deemed: "Not Yet An Adult"
Still a Minor /or Under-aged.
ほぼすべての国には特定の物やサービスに対して厳しいルールがあります。（年齢は１８歳から２１歳の間で国によって異なります）
"to be of legal age" （法的年齢になる）まで酒やタバコ等は購入できません。
日本では２０歳以下は皆、"Not Yet An Adult"（まだ大人ではない）、
Still a Minor /or Under-aged.（まだ未成年）とみなされます。
The words above are all synonyms for someone who is not an adult yet in the eyes of the law.
For example:
1) You cannot drive yet, you are underage!
2) He is still a minor, he must listen to me.
3) He is juvenile.
You may have heard someone call someone else's behavior juvenile? This refers to their behavior and actions being childish.
Thank you for your question!
There are quite a few ways to say this :
minor
underage
adolescent
Examples :
Minors are not allowed to buy alcohol.
Underage drinking and smoking is really bad.
Adolescents can be really difficult at times.
Not all minors are disobedient.
A, "minor," more or less refers to someone who is not an adult yet but it can also refer to someone who is too young to do something like drink alcohol. We can also use the word, "underage(d)," in the exact same way.
When someone is underage they will not be allowed into nightclubs etc, because it is still illegal for them to be drinking alcohol. The legal drinking age varies from country to country. Here is an example: Sorry you are still a minor, you are not allowed in this nightclub. The minimum age here is 21.
You could use any of the above three words to describe a person that is not of age.
- My friend is underage so he is not allowed to drink alcohol.
- When you are under the age of 20 in Japan you are not yet the legal age.
- Anyone under the age of 20 in Japan is a minor.
日本 
イギリス 
南アフリカ 
アメリカ合衆国 
ニュージーランド 
