原げん因いん不ふ明めい

noun, noun which may take the genitive case particle 'no'

cause unknown; of unknown cause

Used in medical, technical, and general contexts to describe a condition, phenomenon, or event whose cause has not been identified.

• 原げん因いん不ふ明めいの熱ねつが続つづいている。

  A fever of unknown cause persists.

• その事じ故こは原げん因いん不ふ明めいのままである。

  The accident remains of unknown cause.