〜とき: How to Say 'When' in Japanese
What it means
とき literally means "time," and it works like the English "when" to set the time frame for an action. You take a clause, put it in plain form, add とき, and then say what happens at that time. Unlike English "when," the word before とき changes shape depending on whether it's a noun, an adjective, or a verb — and verb tense carries real meaning.
子供のとき、ヤッタンは犬が怖かった。
こどもの とき、ヤッタンは いぬが こわかった。
When he was a child, Yattan was scared of dogs.
暇なとき、モチはよく昼寝をする。
ひまな とき、モチは よく ひるねを する。
When she's free, Mochi often takes a nap.
日本語が分からないとき、先生に聞きます。
にほんごが わからない とき、せんせいに ききます。
When I don't understand Japanese, I ask the teacher.
How to form it
The word right before とき goes into plain form. Each word type connects a little differently:
| Word before とき | Connection | Example |
|---|---|---|
| Noun | noun + の + とき | 子供のとき = when (I) was a child |
| な-adjective | stem + な + とき | 暇なとき = when (I'm) free |
| い-adjective | plain form + とき | 忙しいとき = when (I'm) busy |
| Verb | plain form + とき | 食べるとき = when (I) eat |
Note the noun and な-adjective patterns: a noun needs の, and a な-adjective keeps its な (just like before any other noun — because とき is a noun). い-adjectives and verbs simply attach in plain form.
忙しいとき、ヤッタンはご飯を食べない。
いそがしい とき、ヤッタンは ごはんを たべない。
When he's busy, Yattan doesn't eat.
学生のとき、先生は東京に住んでいました。
がくせいの とき、せんせいは とうきょうに すんで いました。
When she was a student, the teacher lived in Tokyo.
The key point: 行くとき vs 行ったとき
This is the part that surprises most learners. The tense of the verb before とき tells you where in the timeline the action happens — and it is set relative to the main action, not relative to now.
- 行くとき (present/plain): the second action happens before or at the moment of going — on the way, or just before you leave.
- 行ったとき (past/た-form): the second action happens after the going is complete — upon arrival, once you're already there.
日本に行くとき、空港でお土産を買います。
にほんに いく とき、くうこうで おみやげを かいます。
When I go to Japan, I'll buy souvenirs at the airport.
行くとき = before arriving — the airport here is the departure airport.
日本に行ったとき、京都でお寺を見ました。
にほんに いった とき、きょうとで おてらを みました。
When I went to Japan, I saw temples in Kyoto.
行ったとき = after arriving — you're already in Japan.
Same trip, two different moments. Use 行くとき for things you do on the way or beforehand, and 行ったとき for things you do once you've gotten there. The same logic applies to other motion and change verbs: 家を出るとき ("when leaving the house," as you go) vs 家を出たとき ("after having left the house").
出かけるとき、モチは鍵を持ちます。
でかける とき、モチは かぎを もちます。
When she goes out, Mochi takes her keys.
出かけるとき — she grabs them as part of leaving (before/at).
家に帰ったとき、ヤッタンの弟は寝ていました。
いえに かえった とき、ヤッタンの おとうとは ねて いました。
When he got home, Yattan's little brother was asleep.
帰ったとき — the sleeping was true after the arrival.
Common mistakes
- Forgetting の after a noun. It's 子供のとき, not 子供とき. A noun always needs の before とき.
- Dropping な on a な-adjective. Say 暇なとき, not 暇とき, because とき is a noun and な-adjectives use な before nouns.
- Always using past tense for past events. Even about the past, 行くとき is correct if the action came before arriving: 日本に行くとき、本を買った ("On my way to Japan, I bought a book"). The tense is relative to the main action, not to now.
- Mixing up 行くとき and 行ったとき. 行くとき = on the way / before; 行ったとき = after arriving. Picking the wrong one changes where the event happens.
Quick recap
- とき = "when." Put the word before it in plain form and add とき.
- Noun + の + とき; な-adj + な + とき; い-adj and verb + plain form + とき.
- 行くとき = before or at the moment of going; 行ったとき = after you've arrived.
- Verb tense before とき is relative to the main action, not to the present.
Your turn
Choose the correct form before とき, including 行くとき vs 行ったとき.
Start the 5-question drill →Frequently asked questions
What's the difference between 行くとき and 行ったとき?
行くとき means the second action happens before or at the moment of going (on the way or just before). 行ったとき means it happens after the going is finished, once you've arrived. Example: 日本に行くとき = buy something at the departure airport; 日本に行ったとき = something you did once already in Japan.
How do I attach とき to a noun?
Add の: 子供のとき ('when I was a child'), 学生のとき ('when I was a student'). The の is required because とき is itself a noun.
Do I keep な on a な-adjective before とき?
Yes. Use な: 暇なとき ('when I'm free'), 元気なとき ('when I'm healthy'). な-adjectives take な before any noun, and とき is a noun.
Does past tense before とき always mean a past event?
No. The tense is relative to the main verb, not to now. 行くとき can describe a past trip if the action came before arriving: 日本に行くとき、本を買った ('On the way to Japan, I bought a book').