Boy, Young Boy, Youth
noun
Someone of few years is someone who's young. Since we already have 少女 for girls, 少年 means boy. 少年 is a bit of a formal term that often refers to a young boy, usually between childhood and adolescence, or sometimes to a youth in general.
しょうねん
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.
これは一人の少年のストーリーです。
This is a story of a boy.
少年マンガは、すきですか？
Do you like boys' manga?
小さいころはスポーツ少年でした。
When I was little, I was a sporty boy.