How to say "observer" in Japanese

• 立会いたちあいCommon
  nounIt names the presence or act of observing — being on hand while something is done — rather than the observer as a person; for a person, 立会人 or オブザーバー is the better choice.
• オブザーバーCommon
  nounThe katakana borrowing of 'observer', for a person: someone present at a meeting, conference, or organization in a non-participating capacity, as with election or international observers.
• 立会人たちあいにんCommon
  nounA person who attends a transaction or procedure in order to watch it — the human counterpart of 立会い; use this when 'observer' means such an attending witness.

For a person called an observer, use 「オブザーバー」 (meetings, monitoring) or 立会人 (someone present to witness a transaction or procedure); 「立会い」 names the presence or act of observing itself, not the person.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 立会いたちあいpresence (e.g. of an observer)
• オブザーバーobserver
• 立会人たちあいにんwitness
• 傍聴人ぼうちょうにんobserver
• 観察者かんさつしゃobserver
• 観測者かんそくしゃobserver
• 監視員かんしいんobserver
• 観者かんしゃobserver
• 傍聴者ぼうちょうしゃobserver
• 視察員しさついんinspector