大事

1. Origins, structure, and basic meaning

• Structure: 大事(だいじ) describes something as important or as an object to be valued and treated with care.
• Basic usage: For importance it appears in 健康が大事です; for careful treatment it appears in 道具を大事に使う.

2. Common pitfalls and similar expressions

• Learn the particles and forms
  • 〜が大事だ commonly states importance, while 〜を大事にする means valuing or taking good care of something.
• Difference from 大切
  • 大切(たいせつ) is a very close synonym meaning important or precious. 大事 is common in everyday judgments and in expressions such as 大事にする.