制約

1. Origins, structure, and basic meaning

• Structure: 制約（せいやく） is a noun for conditions that constrain actions or choices.
• Basic usage: It can name conditions involving time, materials, or construction methods that a plan must account for.

2. Common pitfalls and similar expressions

• What is constrained
  • 時間の制約 identifies time as the constraint; 材料や工法に制約がある describes limited choices of materials and methods.
• Different emphases
  • 制限 often emphasizes a permitted range or limit, while 制約 emphasizes conditions that constrain a choice or action. Their uses can overlap in context.