na-adjective, noun
young and weak; immature and vulnerable
Describes someone or something that is both young and physically weak or inexperienced. Rare and somewhat literary; not an everyday word.
幼弱な子供を守るのは大人の責任だ。
It is the responsibility of adults to protect young and weak children.
その動物の幼弱な個体は捕食者に狙われやすい。
The young and weak individuals of that animal are easily targeted by predators.