youth、teenager、adolescent与 juvenile 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。
- The politician who embodied the hopes of black youth was ousted from office by a vote from members of his own party. It was a sad finale to an otherwise spectacular political career.
这位代表黑人青年希望的政治家被他自己党内的成员投票表决赶下台。对于原本辉煌的政治生涯来说，这是一个惨淡的结局。 - Most countries offer few opportunities for female soccer players, but Norway has a thriving women’s professional league, and the U.S. a burgeoning co-ed youth soccer movement.
大部分国家的女足队员比赛机会不多，但挪威有蓬勃的女足职业联盟，而美国的青年男女混合足球运动正快速发展。
——《时代周刊》 - Warm with the fancies of youth, pretty with the insipid prettiness of the formative period, possessed of a figure promising eventual shapeliness and an eye alight with certain native intelligence, she was a fair example of the middle American class—two generations removed from the emigrant.
她充满着年轻人的热烈幻想。虽然漂亮，她还只是一个正在发育阶段的美人胎子。不过从她的身段已经可以看出将来发育成熟时的美妙体态了。她的眼睛里透着天生的聪明。她是一个典型的美国中产阶级少女——她们家已是移民的第三代了。
——《嘉莉妹妹》（参见：名著下载 | 嘉莉妹妹（Sister Carrie））
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。
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It bombards users with self-repeating clips. It forms a genre of quick-hit entertainment: a prank, a dare, a teenager looking pretty.
它用循环播放的短视频轰炸用户，形成了一种短平快的娱乐类型：恶作剧、大冒险、看起来很漂亮的少男少女。
——《经济学人》 -
他的黑发略有点花白。他甚至在青少年时期就容易情绪抑郁。
His dark hair was just tinged with grey. He was prone to depression even as a teenager.
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。 - 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。
