What Is とき?
とき (時) is a noun meaning “time” or “moment.” In grammar, it is used to connect two clauses and express the idea of “when” — describing the circumstances or timing under which something happens or happened.
💡 とき is a noun, not a conjunction. This is an important distinction from English “when.” Because とき is a noun, the clause that precedes it must modify it like an adjective modifies a noun — using the plain (dictionary) form of the verb, not the polite form.
Basic Structure
Pattern: [Verb 1 in plain form] ＋ とき ＋ [Verb 2]
The clause before とき describes the situation or timing, and the clause after describes what happens during that time.
| Part | Role |
|---|---|
| Verb 1 (plain form) ＋ とき | “when [this situation exists]…” |
| Verb 2 | “…[this] happens / happened” |
Present とき — “When I do X, I do Y”
When the verb before とき is in the plain non-past form, it describes a recurring or general situation — something that is habitually true, or will be true in the future.
Examples:
| Japanese | English |
|---|---|
| わたしはにほんごをべんきょうするとき、ほんをつかいます。 | When I study Japanese, I use a book. |
| わたしはあさごはんをたべるとき、Youtubeをみます。 | When I eat breakfast, I watch YouTube. |
| にほんごをべんきょうするとき、なにをつかいますか？ | What do you use when you study Japanese? |
| かれはいらいらするとき、うさぎをいつもなぐる。 | When he gets irritated, he always hits the rabbit. |
💡 Verb 2 sets the overall tense of the sentence. The verb before とき tells you when, while the verb after とき tells you what happened and when overall. Present とき ＋ present verb = habitual or future situation.
Past とき — “When I did X, I did Y”
When the verb before とき is in the plain past form (た-form), it specifies that the first action was already completed when the second action occurred.
Examples:
| Japanese | English |
|---|---|
| わたしはあさごはんをたべたとき、Youtubeをみました。 | When I had (finished) breakfast, I watched YouTube. |
| うちにかえったとき、ははがいなかった。 | When I got home, my mum wasn’t there. |
| にほんにいったとき、ラーメンをたべました。 | When I went to Japan, I ate ramen. |
The Tense Contrast — This Is the Key Point
The tense of the verb before とき and the tense of the verb after とき are independent of each other, and the combination you choose changes the meaning significantly.
| Verb before とき | Verb after とき | Meaning | Nuance |
|---|---|---|---|
| Non-past (する) | Non-past (する) | When I do X, I do Y | Habitual / general truth |
| Non-past (する) | Past (した) | When I do/did X, Y happened | X was ongoing when Y occurred |
| Past (した) | Past (した) | When I had done X, Y happened | X was completed before Y |
| Past (した) | Non-past (する) | When I have done X, I do Y | X must be complete first |
Illustrative contrast:
日本にいくとき、おみやげをかいました。
When I was going to Japan, I bought souvenirs.
(→ bought them before leaving, while still in the process of “going”)
日本にいったとき、おみやげをかいました。
When I went to Japan (arrived), I bought souvenirs.
(→ bought them after arriving, once the action of going was complete)
💡 This distinction is subtle but important. The plain non-past form before とき suggests the first action was not yet complete when the second occurred. The past form suggests the first action was already completed.
とき with Adjectives and Nouns
とき is not limited to verb clauses. It can also follow adjectives and nouns, using the same rules as other noun-modifying structures.
With い-adjectives (no change needed):
- わかいとき → when (I was) young
- いそがしいとき → when (I am) busy
With な-adjectives (add な):
- ひまなとき → when (I am) free
- げんきなとき → when (I am) well
With nouns (add の):
- こどものとき → when (I was) a child
- がくせいのとき → when (I was) a student
Example sentences:
| Japanese | English |
|---|---|
| こどものとき、よくそとであそんだ。 | When I was a child, I often played outside. |
| ひまなとき、なにをしますか？ | What do you do when you have free time? |
| わかいとき、イタリアにすんでいました。 | When I was young, I lived in Italy. |
Building More Complex Sentences
Once you are comfortable with the basic pattern, you can build longer, more natural sentences by specifying subjects, objects, and destinations.
Step by step:
| Sentence | Japanese |
|---|---|
| When I study → | べんきょうするとき |
| When I study Japanese → | にほんごをべんきょうするとき |
| When I study Japanese, I use a book. → | にほんごをべんきょうするとき、ほんをつかいます。 |
| Sentence | Japanese |
|---|---|
| When I went → | いったとき |
| When I went to Japan → | にほんにいったとき |
| When I went to Japan, I ate sushi. → | にほんにいったとき、すしをたべました。 |
Practice Sentences
Translate the following into Japanese:
- When I watch TV, I eat snacks.
- When I was a student, I studied every day.
- What do you do when you are free?
- When I arrived home, my friend called me.
- When I go to Italy, I want to eat pizza.
Answers:
- テレビをみるとき、おかしをたべます。
- がくせいのとき、まいにちべんきょうしました。
- ひまなとき、なにをしますか？
- うちにかえったとき、ともだちがでんわをかけてきた。
- イタリアにいくとき、ピザをたべたいです。
Summary
| Point | Rule |
|---|---|
| Structure | [Clause in plain form] ＋ とき ＋ [main clause] |
| とき is a noun | The preceding clause modifies とき like an adjective |
| Non-past before とき | First action is not yet complete / habitual |
| Past before とき | First action is already complete |
| Main clause tense | Sets the overall tense of the sentence |
| With い-adj. | い-adjective ＋ とき (no change) |
| With な-adj. | な-adjective ＋ な ＋ とき |
| With nouns | Noun ＋ の ＋ とき |