noun
occasion; time; when; in case of
Used to mark a specific occasion or circumstance, often in formal or written contexts. Functions similarly to 時 (とき) but with a slightly more formal, situational nuance. Commonly appears in the pattern 〜際に or 〜の際は.
お降りの際は、足元にお気をつけください。
Please watch your step when alighting.
非常の際は、このドアを使ってください。
In case of emergency, please use this door.
先日お会いした際に、その書類をお渡ししました。
I handed over the documents when we met the other day.
時 is the general word for 'time' or 'when' and is used broadly in both casual and formal contexts. 際 is more formal and emphasizes the specific occasion or circumstances, often used in set phrases and official announcements.
場合 means 'case' or 'situation' and is used for hypothetical or conditional scenarios. 際 refers more to a concrete occasion or point in time when something happens.
The kanji 際 originally meant 'boundary' or 'juncture', which extended to mean a specific point in time or occasion. The reading さい is the on'yomi.