〜とき: How to Say 'When' in Japanese
The time-frame it links
とき literally means "time," and as a connector it works like the English "when" — it hooks a clause to a moment and says what else is true at that moment. You take a clause, put it in plain form, add とき, and then state the action that shares that time frame. It joins two events on a shared timeline rather than arguing cause or contrast, which makes it the workhorse temporal link of everyday Japanese.
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.
What attaches in front of it
Because とき is itself a noun, the word right before it goes into plain form and connects exactly the way anything else would connect to a noun. Each word type joins 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.
Tense before とき: 行くとき vs 行ったとき
Here is the one restriction that decides what can precede とき in meaning, and it 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.
Watch-outs
- 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.
The short version
- 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.
Practice it
Choose the correct form before とき, including 行くとき vs 行ったとき.
＿＿＿に入れるのに最もよいものを選びなさい。
Choose the grammar pattern that best completes the sentence.
どうするかを決める＿＿＿は、論理ではなく本能を当てにする。
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').
Where 〜とき fits
Don't confuse it with
- 〜から · N5 — から has two everyday jobs: 'because' (giving a reason) and 'from' (a starting point in time or place). Learn how each works, how it differs from ので, with clear examples.
- 〜ので · N5 — 〜ので gives a reason in a soft, polite way ('because…'). Learn how it attaches, how it differs from から, and why it's the safer choice for explanations and excuses.
More N5 grammar to explore
Keep going with related patterns at the same level:
- で — The particle で marks where an action happens, the means or tool you use, the material, the cause, and the scope of a superlative. Learn each use and how で differs from に.
- が — が marks the grammatical subject and introduces new information. Learn how to use が with question words, existence (ある/いる), ability, and likes such as 好き — plus how が differs from は.
- に vs へ — に and へ both mark where you're going: 学校に行く / 学校へ行く. Learn the small nuance, why へ is read 'e', and how に also marks points in time like 7時に.
- は — は marks the topic of a sentence — 'as for X.' Learn how it flags known information, its contrast use, why it's read 'wa,' and how it differs from が.
- 〜ことができる — 〜ことができる expresses ability: dictionary-form verb + ことができる ('can do'). Learn the verb pattern, the noun + ができる pattern, the polite and negative forms, and how it compares to the potential form.
- 〜に行く — 〜に行く/来る/帰る says you go, come, or return somewhere to do something. Learn the ます-stem + に pattern, suru-nouns like 買い物に行く, and how to mark the place.