Translation guide
The English word 'reason' can be expressed in Japanese through several words and patterns, depending on whether you mean a cause, a motive, a logical basis, or an excuse. The most common and versatile word is 理由 (riyuu), but other options like 原因 (gen'in) for cause, わけ (wake) for natural conclusion, and せい (sei) for blame are also important. This guide helps learners choose the right expression for each situation.
Expressing a reason, basis, or grounds for something in a neutral or formal context.
The most common and versatile word for 'reason'. It can be used in both formal and informal settings, and covers a wide range of meanings from cause to excuse.
Please explain the reason for your lateness.
Often used to express a reason that is a natural conclusion or logical outcome. It can also be used to deny a reason or to ask for an explanation. More conversational than 理由.
Refers to circumstances or reasons behind a situation, often implying some complexity or personal circumstances. Used in formal contexts.
Expressing the cause of an event, especially an accident, problem, or natural phenomenon.
Specifically means 'cause' as opposed to 'reason'. Used for the direct cause of an event, often negative or neutral. Not used for personal motives.
Expressing a personal motive, intention, or the reason behind one's actions.
Specifically means 'motive', often used in contexts like crime, decisions, or actions. More formal than 理由 when talking about personal drives.
Expressing a reason that is an excuse or a pretext, often not the real reason.
Expressing a logical basis, rationale, or grounds for a conclusion.
Means 'basis' or 'grounds', often used in arguments, claims, or legal contexts. It refers to the evidence or logical foundation for something.
Expressing 'reason' in the sense of connecting clauses with 'because' or 'since'.
The most common way to say 'because'. It attaches to the plain form of verbs, adjectives, and nouns (with だ/です). It can be used in both casual and polite speech.
理由 (riyuu) is the general word for 'reason' and can be used for both causes and motives. 原因 (gen'in) specifically means 'cause' and is used for events, accidents, or problems. わけ (wake) often implies a logical conclusion or natural reason, and is common in conversational Japanese. Use 理由 when in doubt.
Reason: The reason for being late is oversleeping.
What is the reason he quit?
For that reason, I can't go.
What's the reason you were late? (casual)
I quit the company due to family reasons.
We are investigating the cause of the accident.
The cause of the fire was careless handling of a cigarette.
Used to assign blame or indicate a negative cause. Often translated as 'fault' or 'because of (negative thing)'. It attaches to nouns or plain form verbs/adjectives.
The game was canceled because of the rain. (implying it's the rain's fault)
I was late because of you. (blaming)
What was the motive for the crime?
His motive for running for office was pure.
Also commonly used for personal reasons, though less specific than 動機.
What's the reason you broke up with her?
Means 'excuse' or 'justification'. It often implies that the reason given is not entirely true or is an attempt to avoid blame.
I don't want to hear your excuses.
He's always making excuses.
Means 'pretext' or 'excuse', often used when someone uses a false reason to hide their true intentions. More formal than 言い訳.
He used illness as a pretext to skip the meeting.
There is no basis for that claim.
Please show the scientific basis.
Means 'reasoning' or 'justification', the act of giving reasons. Often used in academic or analytical contexts.
His reasoning is persuasive.
Because it's raining, I'll take an umbrella.
Since I'm tired, I'll go to bed early.
A slightly more formal or polite way to say 'because'. It is often used to give a reason in a softer, more objective manner. Attaches to plain forms, but な-adjectives and nouns use な before ので.
I was late because the train was delayed.
I like it here because it's quiet.
A formal pattern meaning 'because of' or 'due to'. It can be used with nouns (のため) or verbs/adjectives in plain form. Often used in written or official contexts.
Due to the typhoon, the flight was canceled.
Because there was an accident, the road is congested.
Cause: The cause of the accident is speeding.
No wonder he's angry. (lit. It's a reason he gets angry.)
English often uses 'the reason why... is because...', but in Japanese, this structure is redundant. Simply use 理由は〜からです or 理由は〜ことです. Avoid directly translating 'why' as なぜ in this pattern.
The reason I was late is that the train was delayed.