1.
unexpected; unforeseen; unanticipated
Something that was not anticipated or predicted. A literary/formal expression using the classical negative form せぬ (= しない).
予期せぬ事態が起きた。
An unforeseen situation occurred.
予期せぬ来客があって慌てた。
I was flustered by an unexpected visitor.
予期せぬトラブルに備えてバックアップを取っておくべきだ。
You should keep backups in preparation for unforeseen trouble.
USAGE:
予期せぬ is a set phrase functioning as a pre-noun modifier. It uses the classical negative form せぬ (equivalent to しない in modern Japanese), giving it a somewhat formal or literary tone.
GRAMMAR:
Always used before a noun: 予期せぬ + noun. The modern equivalent 予期しない is also used but sounds less natural as a fixed expression. The form 予期せぬ is preferred in writing and formal speech.
VARIATIONS:
- 予期せぬ (classical negative — standard form)
- 予期しない (modern negative — less common as modifier)
- 予期しなかった (past form — "was unexpected")
COMMON COLLOCATIONS:
- 予期せぬ事態 (unforeseen situation)
- 予期せぬ出来事 (unexpected event)
- 予期せぬ結果 (unexpected result)
- 予期せぬ展開 (unexpected development)