打算

1. Origins, structure, and basic meaning

• Structure: 打算(ださん) is a noun for calculating whether something serves one's own interests.
• Basic usage: In discussions of helping people or forming relationships, it can highlight a motive of personal gain.

2. Common pitfalls and similar expressions

• How it differs from 計算
  • 計算(けいさん) is widely used for numerical calculation, while 打算 in these examples focuses on weighing gains and losses behind an action. In the context of choosing friends, calculation for personal advantage is prominent.
• The scope of absence and limitation
  • 打算がなかった means that personal gain was not the motive behind the action, not that the person acted thoughtlessly. だけ in 打算だけで makes self-interest the sole criterion.