〜際(に) / 〜さいに
sai (ni)
By Nihongo PathUpdated
This form is also taught at JLPT N2, where it carries a different sense or register.
Meaning
when… / on the occasion of… (formal)
〜際(に) is a formal way to say "when" or "on the occasion of": お帰りの際は "when leaving", 申し込む際に "when applying". It is the word you hear in announcements, see on forms, and read in business emails. In casual conversation people simply say 〜とき.
Announcements, notices, official instructions, business letters, and polite explanations. Not used for trivial daily actions (×ご飯を食べる際).
Formation
V = verb, N = noun, A = adjective.
Verb (dictionary form / た-form) + 際(に)Noun + の + 際(に)Set forms: 〜の際は / 〜する際には / この際 (this occasion)Honorific: お〜の際 (お帰りの際, ご利用の際)
Visual diagram
〜とき
Neutral; everyday use.
〜場合
'In the case that'; hypothetical or conditional.
〜際(に)
Formal 'on the occasion of'; announcements and business.
〜に際して (N2)
Very formal; ceremonies and official documents.
〜とき
Neutral; everyday use.
〜場合
'In the case that'; hypothetical or conditional.
〜際(に)
Formal 'on the occasion of'; announcements and business.
〜に際して (N2)
Very formal; ceremonies and official documents.
Natural examples
お帰りの際は、忘れ物にご注意ください。
おかえりのさいは、わすれものにごちゅういください。
When leaving, please be careful not to forget anything.
Announcement style: お〜の際は.
申し込む際に、身分証明書が必要です。
もうしこむさいに、みぶんしょうめいしょがひつようです。
When applying, you need identification.
Instruction on a form: 申し込む際に.
日本を訪れた際に、京都にも行った。
にほんをおとずれたさいに、きょうとにもいった。
When I visited Japan, I also went to Kyoto.
Past event: 訪れた際に.
ご利用の際は、会員カードをご提示ください。
ごりようのさいは、かいいんカードをごていじください。
When using the service, please show your membership card.
ご + noun + の際は: typical notice.
契約する際には、内容をよく確認してください。
けいやくするさいには、ないようをよくかくにんしてください。
When signing a contract, please check the contents carefully.
する verb + 際には.
Similar grammar and the difference
〜とき
Everyday equivalent; 際 is formal and limited to notable occasions.
〜場合
'In case of' — describes a possible situation rather than an occasion (雨の場合).
〜に当たって / 〜に際して
Even more formal, for the start of an important undertaking (N2).
Common mistakes
- ✗
- 朝ご飯を食べる際に、テレビを見る。
- ✓
- 朝ご飯を食べるとき、テレビを見る。
- Why
- 際 is for formal or notable occasions, not routine daily actions.
- ✗
- お帰り際は
- ✓
- お帰りの際は
- Why
- Nouns need の before 際. (帰り際 without の is a different word meaning 'just as one is leaving'.)
- ✗
- 困った際にに
- ✓
- 困った際に(は)
- Why
- 際に already contains に; do not double it.
この際 means 'on this occasion / while we're at it' (この際、はっきり言おう). 際 can be followed by は, に, には, or nothing. Announcements often pair it with honorific verbs: お越しの際は, ご来店の際は.
JLPT N3 tips
On the exam
- A formal notice or business sentence with a blank meaning 'when' → 際.
- If the choices include とき and 際 and the register is polite/formal, choose 際.
- Look for の after a noun before 際; 際 directly after a noun is a trap.
Frequently asked questions
What does 〜際(に) / 〜さいに mean?
when… / on the occasion of… (formal). 〜際(に) is a formal way to say "when" or "on the occasion of": お帰りの際は "when leaving", 申し込む際に "when applying". It is the word you hear in announcements, see on forms, and read in business emails. In casual conversation people simply say 〜とき.
How do you form 〜際(に) / 〜さいに?
Verb (dictionary form / た-form) + 際(に) / Noun + の + 際(に) / Set forms: 〜の際は / 〜する際には / この際 (this occasion) / Honorific: お〜の際 (お帰りの際, ご利用の際). V = verb, N = noun, A = adjective.
When is 〜際(に) / 〜さいに used?
Announcements, notices, official instructions, business letters, and polite explanations. Not used for trivial daily actions (×ご飯を食べる際).
What is the difference between 〜際(に) / 〜さいに and 〜とき?
Everyday equivalent; 際 is formal and limited to notable occasions.
What is the difference between 〜際(に) / 〜さいに and 〜場合?
'In case of' — describes a possible situation rather than an occasion (雨の場合).
What is a common mistake with 〜際(に) / 〜さいに?
Wrong: 朝ご飯を食べる際に、テレビを見る。 Right: 朝ご飯を食べるとき、テレビを見る。 際 is for formal or notable occasions, not routine daily actions.
Quick check
お降り（ ）は、足元にご注意ください。