私的

1. Origins, structure, and basic meaning

• Structure: 私的 is an adjectival noun read してき, meaning private or personal rather than public or official. Use 私的な before a noun and 私的に to modify an action.
• Basic usage: It distinguishes private purposes from public or organizational ones, such as personal use of company equipment or bringing private feelings into an official meeting.
  • 会社の設備を私的に使ってはいけない。 prohibits using company equipment for personal purposes; 会議では私的な感情を持ち込まないようにした。 describes trying not to bring personal feelings into a meeting.

2. Common pitfalls and similar expressions

• 私的に使う
  • The に form modifies 使う and identifies the purpose or manner of use as private; it does not say that the equipment is privately owned.
• 私的な感情
  • な links the adjectival noun to 感情, forming the phrase personal feelings.
• 私的 and 個人的
  • Both can concern an individual, but 私的 especially highlights a private character in contrast with a public or official purpose.