这些名词均有“年轻人，青少年”之意。

youth : 现在几乎专指男青年，尤指10多岁到20多一点的男青年，但作为集合名时间男女青年都可指。

I was a fairly good football player in my youth.

我年轻时是个相当不错的足球运动员。

The first volume is the author's account of his misspent youth in the bars of Dublin.

第一卷是作者对他在都柏林酒吧里虚度青春的叙述。

He looks like a man who's found the secret to eternal youth (= staying young).

他看上去似乎掌握了永葆青春的秘诀。

You may not have played tennis as often as him, but at least you've got youth on your side (= you are young).

你可能没像他那样经常打网球，但至少你有年轻的优势。

teenager : 主要指13岁到19岁之间的青少年，强调这个年龄段的人的本身特点。

The magazine is aimed at teenagers and young adults.

这份杂志的读者对象是青少年和二十来岁的年轻人。

adolescent比teenager正式，侧重年龄。

It is important that an adolescent boy should have an adult in whom he can confide.

关键是，青春期的男孩身边应该有一个可以交心的成年人。

Parents worry about the effect of music on their adolescent's behavior.

父母担心音乐对青春期孩子的行为所产生的影响。

juvenile : 指青少年，系法律上的常用词。

Juvenile crime is increasing at a terrifying rate.

青少年犯罪正在以惊人的速度增长。

He is an expert in juvenile delinquency.

他是研究青少年犯罪的专家。

This juvenile offender received no more than a judicial slap on the wrist.

这名少年犯只被从轻处惩了一下。