とき (When) in Japanese

In Brief

Use とき after a plain-form verb, adjective, or noun phrase to mean “when” or “at the time that”: 出かけるとき “when leaving,” 忙しいとき “when busy,” and 子供のとき “when I was a child.” With verbs, the form before とき shows whether that action is complete at the time of the main event: 行くとき usually means before or while going, while 行ったとき looks back on the completed trip or arrival.

Overview

とき (時 in kanji) is a noun meaning “time.” A clause or descriptive phrase can be placed before it, creating a larger expression that identifies a time: 日本に行くとき literally has the shape “the time of going to Japan.” That whole expression then tells you when the main action happens.

This is a central A2 pattern because it works with verbs, い-adjectives, な-adjectives, and nouns. An adjective is a word that describes a quality, such as “cold” or “quiet”; a noun names a person, thing, role, or idea, such as “child” or “student.” Once you know the Japanese plain forms, you can use とき to talk about routines, memories, plans, and conditions.

English often chooses the tense of both clauses according to the overall time of the story. Japanese works differently: the form immediately before とき primarily shows how that event or state relates to the event in the main clause. This difference matters most with verbs and is the main point to master.

How It Works

The basic sentence shape

The とき phrase can come before or after the main clause:

• [situation] + とき、[main event]。
• [main event] + のは、[situation] + ときです。

For example, 暇なとき、本を読みます means “When I am free, I read.” Japanese often leaves out a subject such as “I” when context makes it clear.

Forms used before とき

Word type	Pattern	Example	Meaning
Verb, nonpast	plain nonpast + とき	行くとき	when going / when about to go
Verb, past	plain past + とき	行ったとき	when someone went / after arriving
い-adjective	adjective + とき	寒いとき	when it is cold
Past い-adjective	～かった + とき	寒かったとき	when it was cold
な-adjective	adjective + な + とき	暇なとき	when free
Past な-adjective	adjective + だった + とき	暇だったとき	when one was free
Noun	noun + の + とき	子供のとき	when one was a child
Past noun statement	noun + だった + とき	学生だったとき	when one was a student

The links な and の are essential. Use 静かなとき, not 静かのとき, and 学生のとき, not 学生なとき.

Negative forms work in the same way:

• 時間がないとき — when there is no time
• 元気ではないとき — when one is not well
• 学生ではなかったとき — when one was not a student
• 分からなかったとき — when one did not understand

Polite style normally appears in the main clause, while the clause before とき remains plain: 分からないとき、先生に聞きます. In very formal speech, a polite form before とき is possible, but the plain pattern is the natural default learners need.

行くとき and 行ったとき: relative timing

Consider two events: going to Japan and buying a guidebook.

Japanese	Likely sequence	Natural interpretation
日本に行くとき、ガイドブックを買いました。	buy → go	I bought a guidebook when I was going to Japan / before the trip.
日本に行ったとき、ガイドブックを買いました。	go or arrive → buy	I bought a guidebook when I went to Japan / once there.

The main verb 買いました is past in both sentences. The difference comes from the verb before とき:

• 行く is nonpast, so going is not yet treated as complete at the guidebook-buying time.
• 行った is past, so going is treated as complete at that reference time.

This is relative tense: tense viewed in relation to another event, rather than simply in relation to the moment of speaking. The contrast is often “before completion” versus “after completion,” not a mechanical English present-versus-past contrast.

The exact boundary depends on the verb and real-world context. With an action that takes time, a nonpast form can also mean during its beginning or course: 寝るとき、電気を消します means “I turn off the light when I go to bed,” normally just before sleeping. 寝たとき describes a time when sleeping or falling asleep is already established.

States and repeated situations

With adjectives and nouns, choose a form that presents the state naturally:

• 寒いとき、コートを着ます。 — I wear a coat when it is cold.
• 子供のとき、よく川で遊びました。 — When I was a child, I often played by the river.
• 学生だったとき、京都に住んでいました。 — When I was a student, I lived in Kyoto.

Both 学生のとき and 学生だったとき can refer to a past student period. 学生のとき simply labels the period “when I was a student”; 学生だったとき explicitly presents being a student as a past state. The shorter noun + の pattern is extremely common.

Particles after とき

A particle is a short word that marks the role of a phrase. とき can stand without another particle, or take one when the sentence requires it.

Form	Typical role	Example
～とき	general “when”	暇なとき、本を読みます。
～ときに	a particular point or occasion	家を出るときに、電話が鳴りました。
～ときは	the time/situation as topic or contrast	困ったときは、連絡してください。
～ときの + noun	describes another noun	子供のときの写真

に often highlights the time at which an event occurs, but it is frequently optional. Do not assume every English “when” needs に. With a time span, habit, or broad condition, no に is often more natural. は presents the situation as a topic—roughly “as for times when…”—and is common in advice and general rules.

Examples in Context

Japanese	English	Note
日本に行くとき、ガイドブックを買いました。	When going to Japan, I bought a guidebook.	The purchase was before the trip was complete.
日本に行ったとき、京都にも行きました。	When I went to Japan, I also went to Kyoto.	The trip is viewed as an established event.
暇なとき、何をしますか？	What do you do when you are free?	な-adjective + な
子供のとき、よく外で遊びました。	When I was a child, I often played outside.	Noun + の
寒いとき、温かい飲み物が欲しいです。	When it is cold, I want a warm drink.	い-adjective directly before とき
忙しかったとき、友達が手伝ってくれました。	When I was busy, a friend helped me.	Past い-adjective
分からないときは、先生に聞いてください。	When you do not understand, please ask the teacher.	は frames general advice.
駅に着いたとき、雨が降っていました。	When I arrived at the station, it was raining.	Arrival was complete at the reference time.
駅に着くとき、電話してください。	Call me when you are about to arrive at the station.	Arrival is not yet complete.
寝るとき、スマートフォンを見ません。	I do not look at my phone when I go to bed.	A bedtime routine.
家を出るときに、鍵を確認しました。	I checked the lock when I left the house.	に focuses on that occasion.
学生だったとき、毎日この店で昼ご飯を食べました。	When I was a student, I ate lunch at this restaurant every day.	Explicit past state.
旅行のときの写真を見せてください。	Please show me the photos from the trip.	ときの modifies 写真.
時間がないときは、朝ご飯を食べません。	When I have no time, I do not eat breakfast.	Negative plain form.

Common Mistakes

Using polite ます before とき as the default

• Unnatural for the basic pattern: 日本に行きますとき、写真を撮ります。
• Right: 日本に行くとき、写真を撮ります。
• Why: Use the plain form before とき, even when the main clause is polite. ます belongs naturally on the sentence-final verb here.

Dropping な after a な-adjective

• Wrong: 暇とき、本を読みます。
• Right: 暇なとき、本を読みます。
• Why: A な-adjective needs な when it directly describes とき.

Using の after an い-adjective

• Wrong: 寒いのとき、コートを着ます。
• Right: 寒いとき、コートを着ます。
• Why: An い-adjective attaches directly. の belongs in the basic noun pattern, as in 子供のとき.

Choosing verb tense only from the overall past time

• Misleading: 日本に行ったとき、空港で円を買いました。 when you mean that you bought yen before departure
• Right for that sequence: 日本に行くとき、空港で円を買いました。
• Why: The verb before とき shows whether going is complete at the time of buying. A past main clause does not automatically require a past verb before とき.

Adding に every time

• Awkward as a general habit: 暇なときに、いつも本を読みます。
• More neutral: 暇なとき、いつも本を読みます。
• Why: に is possible in many sentences, but it tends to focus on a time point or occasion. Broad conditions and habits often need no particle after とき.

Usage Notes

Japanese writes both とき and 時. Hiragana is common in learner materials and when the expression functions like a grammatical connector. The kanji is also normal, especially when “time” feels more noun-like. The grammar and pronunciation are the same.

English “when” can introduce a question as well as a time clause. Japanese does not use とき alone for “when?” Use いつ: いつ日本に行きますか means “When will you go to Japan?” Use とき when you attach a situation to a time: 日本に行くとき、何を持って行きますか means “What will you take when you go to Japan?”

Subjects can differ across the two clauses. 私が帰るとき、母は料理をしていました means “When I returned, my mother was cooking.” When a subject must be stated inside the とき clause, が commonly marks it; は often sets the broader topic or creates contrast.

Beyond the Basics / Advanced Use

You do not need to master all of these distinctions at A2, but you will meet them later.

とき versus たら

Both can translate as “when.” とき identifies a time or circumstance and works well for routines, background, and descriptions. ～たら often presents one event as completed before the next event or means “once/if that happens.” Compare:

• 東京に行くとき、友達に連絡します。 — I will contact my friend when going to Tokyo, possibly before departure.
• 東京に行ったら、友達に連絡します。 — Once I get to Tokyo, I will contact my friend.

This makes たら especially useful when the second action clearly follows the first.

とき versus 間 and うちに

とき points to a time or situation, but it does not by itself emphasize the whole duration. 間 means “during the whole interval,” while 間に places an event somewhere within that interval:

• 日本にいるとき、温泉に行きました。 — When I was in Japan, I went to a hot spring.
• 日本にいる間、日本語を毎日使いました。 — Throughout my stay in Japan, I used Japanese every day.
• 日本にいる間に、温泉に行きました。 — During my stay in Japan, I went to a hot spring.

うちに often means “while the opportunity or state still lasts,” as in 若いうちに旅行したい (“I want to travel while I am still young”).

Formal alternatives

Public notices, business writing, and formal speech often use 際（さい） instead of everyday とき: お越しの際は、ご連絡ください means “Please contact us when you come.” 折（おり） is more literary or ceremonious. These are register choices, not direct upgrades that should replace とき in ordinary conversation.

Practice Tips

1. Build four-part sets. Choose one verb and make nonpast, negative, past, and past-negative phrases: 行くとき・行かないとき・行ったとき・行かなかったとき. Add a short main clause to each.
2. Draw the event order. For pairs such as 出るとき／出たとき, mark which event happens first. This is more reliable than translating English tense word for word.
3. Rotate word types. Describe one day using a verb, an い-adjective, a な-adjective, and a noun: 起きるとき, 寒いとき, 暇なとき, 学生のとき. Say the linking sound aloud so な and の become automatic.

Related Concepts

• Prerequisite: Plain/Dictionary Form — supplies the verb forms used before とき.
• Next steps: 際・折・時 (Formal “When”) — expands the pattern into formal and literary registers.