不足

1. Origins, structure, and basic meaning

• Structure: 不足 (ふそく) is an action and state noun for lacking a required amount, activity, or information.
• Basic usage: 運動不足を解消する concerns an insufficient amount of physical activity, while 説明が不足していた makes missing information the cause of misunderstanding.

2. Common pitfalls and similar expressions

• Lack of activity and lack of information
  • 運動不足 measures activity, whereas 説明が不足する measures conveyed information. The latter does not necessarily mean that no explanation was given at all.