1.youth的基本意思是“青少年时期”,也可指“青春”“活力”“朝气”“血气”,是不可数名词,作主语时,谓语动词只能用单数形式。
2.youth还可作“青年人”解,指某个地区、国家或特定时期男女青年的总称,是集合名词,通常用作单数形式,其前常有定冠词the修饰,其后多与介词of连用,作主语时,谓语动词通常用复数形式,有时也用单数形式。
3.youth也可作“青年男子,小伙子”解,是可数名词。

in the first/full flush of youth
在青春初期,在初发阶段 in the freshness or vigour, etc.; at its beginning
In the full flush of youth, nothing was an obstacle.在成就如日中天时,其锐势不可挡。
He was killed in an aeroplane accident in the first flush of youth.他在风华正茂时期因飞机失事身亡。

He spent his youth in the north.他在北方度过了青年时代。
They studied together in their youth.青少年时期他们就在一起学习。
In his youth, he had shown great promise.他在青年时代就显示出前途无量。
He is a friend of my youth.他是我青年时代的一个朋友。
He sighed for the lost days of his youth.他哀叹失去的青春年华。
I am determined to give my youth to the motherland.我决心把青春献给祖国。
He lost his youth a long time ago.他早已失去了青春活力。
She's trying frantically to maintain her youth.她千方百计试图保持年轻。
Old Beijing is full of youth and vigour.古老的北京充满青春活力。
When you're older you'll be sorry that you idled away your youth instead of preparing for a profession.等你老了你会为你虚度了青春而没有认真从事一项事业而后悔。
Spartan youth were bred as warriors.斯巴达的青年被训练成武士。
The youth of the country is/are being ignored by politicians.这个国家的青年人没有受到政治家们的重视。
It is necessary to get the youth to have a high ethical concept.必须使青年具有高度的道德观念。
The youth admitted that he had stiffed horses for a fee.这个青年承认他为了钱而对一些马作了手脚,使它们跑得不快。
As a youth he showed little promise.他这个小伙子,看不出有什么出息。
Both her brothers are tall fair-haired youths.她的两个兄弟都是个子高大、有着金黄色头发的青年。
The fight was started by some youths who had been drinking.这场架是一帮喝醉了酒的小青年惹起的。
Vigorous youth is subjected to rigorous discipline.使活泼的年轻人受严格的纪律约束。
He billeted in youth hotels.他投宿于青年旅店。
The children don't do much at their youth club, but at least it keeps them out of harm's way.虽说孩子们在青少年俱乐部里也干不了什么,但在那儿起码可以不出事儿。

a youth, a young man
两者意思不同:a youth指青春发育期至成年时期的男青年,一般指20岁以下的“男青年”; a young man则指21岁至30岁左右的男子。例如:
When still a youth, he had to make a living by himself.年轻的时候他就不得不一个人谋生。
Most colorful were the young men and women.最显得绚丽多彩的是那些男女青年。

1.一些年轻人正站在车站旁边。
［误］  Some youth were standing near the bus stop.
［正］  Some youths were standing near the bus stop.
［析］  当youth作“年轻人”解时,它是可数名词,词尾可加-s。如果要说“一个年轻人”,可以用a youth来表达。
2.这个国家的青年都斗志昂扬。
［误］  The youths of the country are ready to fight.
［正］  The youth of the country are ready to fight.
当代的青年人不知道自己想要什么。
［误］  The youth of today doesn't know what he wants.
［正］  The youth of today don't know what they want.
［析］  youth前面加定冠词the表示特定地区或特定时期的“青年们”,是集合名词,词尾不加-s。用作主语时谓语动词常用复数形式。
3.她的青春是在苏格兰度过的。
［误］  She spent her youths in Scotland.
［正］  She spent her youth in Scotland.
［析］  表示一个人的“青春”“青年时代”时, youth是不可数名词,没有复数形式。

［同义词］   adolescence, child, lad, stripling, teenager, youngster, lass
［反义词］   adult, grown-up
［词源］  ＜古英语geoguth,geong(青年,年轻)