When translating "when" into Japanese, most learners default to 〜時. But Japanese actually has three options: 時, 場合, and 際, each with very different nuances and appropriate contexts. This article compares five groups of commonly confused nouns to help you build more precise vocabulary instincts.
時 vs 場合 vs 際: The "When" Trio
| Word | Reading | Core Meaning | Formality |
|---|---|---|---|
| 時 | とき | a point/period in time | everyday |
| 場合 | ばあい | a situation/condition | neutral |
| 際 | さい | on the occasion of | formal/written |
時: The All-Purpose "When"
時 is the most everyday option and works in almost any context:
子供の時、よく公園で遊びました。 → When I was a child, I often played in the park.
日本に行った時、富士山を見ました。 → When I went to Japan, I saw Mt. Fuji.
場合: Emphasizing "In the Case That"
場合 is not purely about time — it emphasizes "under a certain condition/circumstance." It's closer to "in case" or "if the situation is":
雨の場合、試合は中止です。 → In case of rain, the match will be cancelled.
わからない場合は、先生に聞いてください。 → If you don't understand, please ask the teacher.
Key point: 場合 implies a hypothetical — you're not sure whether this situation will arise. 時 is more neutral and can refer to things that already happened.
際: "On the Occasion Of" — For Formal Contexts
際 is the most formal of the three, typically found in written notices, instructions, and announcements:
お帰りの際は、忘れ物にご注意ください。 → When leaving, please make sure you haven't forgotten anything.
ご利用の際は、身分証明書をお持ちください。 → When using this service, please bring identification.
You would almost never use 際 in casual conversation. Dropping it into a chat with friends would sound stiff and robotic.
Comparison Table
| Context | 時 | 場合 | 際 |
|---|---|---|---|
| Casual conversation | OK | OK | Unnatural |
| Describing past experiences | OK | Unnatural | Unnatural |
| Hypothetical situations | OK | Best fit | OK (written) |
| Formal notices/instructions | OK | OK | Best fit |
理由 vs 原因 vs わけ: Three Layers of "Reason"
| Word | Reading | Core Meaning | Feel |
|---|---|---|---|
| 理由 | りゆう | subjective reason, justification | personal |
| 原因 | げんいん | objective cause, root factor | factual |
| わけ | — | explanation, how things are | conversational |
遅刻した理由を教えてください。 → Please tell me the reason you were late. (Your personal justification)
事故の原因を調べています。 → We are investigating the cause of the accident. (Objective root cause)
どういうわけか、電気がつかない。 → For some reason, the lights won't turn on. (Can't figure out why)
Quick Decision Guide
- Something you can ask "why did you...?" about → 理由 (personal judgment)
- Something requiring investigation to determine → 原因 (objective causation)
- A "what's going on here?" feeling → わけ (unclear explanation)
気持ち vs 気分 vs 機嫌: The Mood Trio
| Word | Reading | Core Meaning | Duration |
|---|---|---|---|
| 気持ち | きもち | feelings, emotions | short or long |
| 気分 | きぶん | mood, (physical) feeling | temporary |
| 機嫌 | きげん | temper, visible mood | outward display |
彼の気持ちがわかります。 → I can understand his feelings. (Deep inner emotions)
今日は気分がいいです。 → I'm in a good mood today. (Current emotional/physical state)
部長は今日、機嫌が悪いです。 → The manager is in a bad mood today. (Observable emotional state)
Key Differences
- 気持ち is the broadest — it can mean deep feelings (love, gratitude) or momentary sensations (nausea, comfort)
- 気分 often connects to physical state: 気分が悪い can mean "feeling moody" or "feeling nauseous/unwell"
- 機嫌 is only used to describe someone's outwardly displayed mood, commonly as 機嫌がいい/悪い (in a good/bad mood)
意味 vs 意義: Meaning vs Significance
| Word | Reading | Core Meaning | Example |
|---|---|---|---|
| 意味 | いみ | meaning of a word/sentence | この言葉の意味がわかりません。 |
| 意義 | いぎ | deeper significance, value | この研究には大きな意義がある。 |
The mapping is fairly straightforward:
- 意味 = meaning (What does this word mean?)
- 意義 = significance (What is the significance of this?)
人生の意味 (the meaning of life) → leans toward "definition" 人生の意義 (the significance of life) → value, what makes it worth living
方法 vs やり方 vs 仕方: The "Method" Formality Ladder
| Word | Reading | Formality | Context |
|---|---|---|---|
| 方法 | ほうほう | formal | academic papers, work reports |
| やり方 | やりかた | casual | between friends, everyday talk |
| 仕方 | しかた | neutral | both written and spoken |
新しい方法を開発しました。 → We developed a new method. (Academic/professional)
やり方を教えて。 → Show me how to do it. (Between friends)
仕方がない。 → It can't be helped. (Fixed expression, extremely common)
Note: 仕方がない ("it can't be helped" / "nothing we can do about it") is an ultra-common fixed expression that practically every Japanese person uses daily. Its casual contraction is しょうがない.
Formality Ladder
方法 (formal) > 仕方 (neutral) > やり方 (casual)
Summary
- 時 vs 場合 vs 際: everyday time point vs hypothetical condition vs formal occasion
- 理由 vs 原因 vs わけ: subjective justification vs objective cause vs "what's going on?"
- 気持ち vs 気分 vs 機嫌: inner feelings vs current mood/physical state vs outwardly displayed temper
- 意味 vs 意義: word meaning vs deeper significance
- 方法 vs やり方 vs 仕方: formal method vs casual "how-to" vs neutral way (仕方がない = can't be helped)
Practice Quiz
Q1. Translate: "In case of rain, the event will be held indoors." — Which is most appropriate: 時, 場合, or 際?
Show Answer
雨の場合、イベントは室内で行います。
This describes a hypothetical condition (what if it rains), so 場合 fits best. Using 時 wouldn't be wrong, but 場合 more precisely conveys "under this condition."
Q2. Your friend wants to know what a kanji character means. Should they ask using 意味 or 意義?
Show Answer
この漢字の意味は何ですか。
Use 意味 for the meaning/reading of a word. 意義 is for deeper significance or value — overkill for asking what a character means.
Q3. A coworker was late, and the boss wants an explanation. Which is most natural: 理由, 原因, or わけ?
Show Answer
遅刻した理由を説明してください。
The boss is asking "why were you late?" and expects a personal explanation/justification, so 理由 is the most natural choice. If you were investigating why a traffic accident happened, you'd use 原因.