幼い

1. Origins, structure, and basic meaning

• Structure: 幼い(おさない) is an adjective describing a very young age or immature thinking and behavior.
• Basic usage: It asks someone to keep watching a young child.
  • 幼い子どもから目を離さないでください。

2. Common pitfalls and similar expressions

• Contrast with 若い
  • 若い(わかい) can describe young adults as well. 幼い is more suited to a child's young age or to a similar lack of maturity.
• Childhood and immature thinking
  • 幼いころ refers to one's early childhood. 考え方が幼い focuses on an assessment of immature thinking rather than on chronological age.