for any reason; no matter what the reason
Used in negative or restrictive contexts to mean 'for no reason whatsoever' or 'regardless of the reason'. Often appears as いかなる理由があっても or いかなる理由でも.
Violence is not acceptable for any reason whatsoever.
No matter what the reason, being late is being late.
More casual and conversational than いかなる理由, which is formal and emphatic.
Similar formal expression meaning 'in any case' or 'under any circumstances', while いかなる理由 focuses specifically on reasons.
Standard modern spelling using kana for いかなる and kanji for 理由.
Formal or literary spelling using the kanji 如何; less common in everyday writing.
Combination of the formal interrogative いかなる (how, what kind of) and the noun 理由 (reason). いかなる derives from classical Japanese 如何なる, a literary form still used in formal modern contexts.