Youth
Young Man, Young Adult
noun
Someone who is in their young years is a youth, or young man.
青年 refers to young adults, usually in their late teens to early twenties. The word is gender-neutral in legal or official contexts, but in everyday use 青年 usually refers to young men.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. That said, this reading can be easy to confuse with other similar words, so here's a mnemonic to help you out:
The youth like to play with sabers (せい) and nendoroids (ねん). Think about it: as you leave childhood and become a 青年, you want more mature and dangerous hobbies, right? So you move on from plastic swords and soft toys to playing with real sabers and nendoroid action figures. You're such a cool 青年.
その青年は十八才でした。
The young man was eighteen years old.
あなたは、なんて心の広い青年だ。
What a generous young man you are.
青年は大人になったらパイロットになりたいと言っていた。
The young man said he wanted to be a pilot when grows up.