noun
youngster; young person; immature person
Refers to a young person, often with a nuance of inexperience or immaturity. The reading じゃくねんもの is less common and may carry a slightly more colloquial or dated feel.
若年者の失業率が高い。
The unemployment rate among young people is high.
彼はまだ若年者だから、判断が甘い。
He's still a youngster, so his judgment is naive.
Compound of 若年 (jakunen, 'young age') + 者 (sha, 'person'). The reading じゃくねんもの uses the native Japanese suffix 者 (mono) instead of the Sino-Japanese 者 (sha).