理由(りゆう)

理由(りゆう) is a straightforward, somewhat formal noun meaning "reason" or "grounds." It is used when explicitly stating or asking about the reason for something.

Common patterns

• ～の理由(りゆう): the reason for ~
• 理由(りゆう)を聞(き)く: to ask for a reason
• 理由(りゆう)を述(の)べる: to state a reason
• 理由(りゆう)なく: without reason
• 理由(りゆう)があって: for a reason

Similar words

• 理由(りゆう): reason, justification (formal, explicit)
• わけ: reason (conversational, often in grammatical patterns)
• 原因(げんいん): cause (objective, scientific/technical)
• 動機(どうき): motive (for actions, especially crimes)

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Appropriate for both spoken and written Japanese. More formal than わけ and commonly used in business, academic, and official contexts.