Ordering events in time

A learner who can build a clause in front of a noun already owns every time expression in Japanese, because 時とき, 前まえ, 後あと and 間あいだ are ordinary nouns and a time clause is just a clause modifying one of them. The only genuinely new thing in this lesson is a rule about tense, and that rule turns out to explain three constructions at once.

A time clause is a noun-modifying clause

時とき means "time" or "occasion". Put a plain clause in front of it, exactly as the previous lesson did with 本ほん and 人ひと, and you get "the time when that happened", which is what English calls a when-clause.

国くにに帰かえる時とき、空港くうこうで電話でんわする kuni ni kaeru toki, kuukou de denwa suru when I go back to my country, I'll ring from the airport

Because 時とき is a noun, everything that can modify a noun can modify it. Verbs use the plain form, い adjectives attach directly, な adjectives take な and nouns take の.

子こどもの時とき、よく川かわで遊あそんだ kodomo no toki, yoku kawa de asonda when I was a child, I often played in the river

暇ひまな時ときは何なにをしますか hima na toki wa nani o shimasu ka what do you do when you're free?

若わかい時ときによく旅行りょこうをした wakai toki ni yoku ryokou o shita I travelled a lot when I was young

That is the whole construction. The particle after 時とき follows the ordinary rules: に pins it to a point, は contrasts it with other occasions, and bare 時とき followed by a comma is the commonest of all.

The tense inside a time clause is relative

Now the part that surprises everyone. The verb in front of 時とき is not marked for whether the event is in the past. It is marked for whether the event has already happened at the moment the main clause describes. Compare these two, which differ by a single kana and describe different holidays.

日本にほんに行いく時とき、カメラを買かった nihon ni iku toki, kamera o katta when I went to Japan, I bought a camera (before setting off, or on the way)

日本にほんに行いった時とき、カメラを買かった nihon ni itta toki, kamera o katta when I went to Japan, I bought a camera (once I was there)

Both are in the past overall, and the main verb 買かった says so in both. The 時とき clause says something else. In the first, at the moment of buying, the going to Japan had not yet happened, so it stands in the nonpast; the camera was bought at home or in the departure lounge. In the second, at the moment of buying, the going had happened, so it stands in the past; the camera was bought in Japan.

This is why English translations of Japanese textbooks so often gloss both as "when I went". English tense is anchored to the moment of speaking. Japanese subordinate tense is anchored to the main clause. Once you accept that single difference the rest of this lesson costs nothing, because the other constructions are the same rule with the freedom taken away.

Example. Choose the right form: 家いえを（出でる／出でた）時とき、かぎをかけた, meaning "I locked the door when I left the house".

You lock a door from the outside, after leaving, so at the moment of locking the leaving has already happened: 出でた時とき. Choosing 出でる時とき is not ungrammatical, but it describes locking something while still inside, which would be a different door. This pair is the standard classroom demonstration precisely because both versions are possible sentences about the real world and the grammar picks out which one you meant.

Now you. Choose the right form and say what the other one would mean: ごはんを（食たべる／食たべた）時とき、「いただきます」と言いう.

まえに and あとで are the same rule

前まえ means "the front" or "before", 後あと means "after". Both are nouns, both take clauses in front of them, and both look at first like exceptions because their tense is fixed. They are not exceptions. They are the 時とき rule with no choice left.

まえに always takes the dictionary form, whatever the tense of the main clause.

寝ねる前まえに歯はを磨みがいた neru mae ni ha o migaita I brushed my teeth before going to bed

Ask why, and the answer writes itself: at the moment of brushing, the going to bed had not happened. That is exactly what "before" means. A past form there would be a contradiction, which is why 寝ねた前まえに is not a stylistic slip but nonsense.

あとで always takes the past form, again whatever the main clause does.

晩ばんごはんを食たべた後あとで、映画えいがを見みます bangohan o tabeta ato de, eiga o mimasu I'll watch a film after eating dinner

The main verb is nonpast, and the meal is still in the future at the moment of speaking, yet 食たべた is past, because at the moment of watching the film the meal will be over. One rule, two constructions, no memorisation.

Nouns work with both, joined by の: 食事しょくじの前まえに, before the meal; 授業じゅぎょうの後あとで, after the lesson.

てから, and counting time since

てから is built from the て form you already have, plus から, and it does two jobs that are worth keeping apart.

The first is sequence with a sense of prerequisite. 手てを洗あらってから食たべてください, wash your hands and then eat, presents the washing as something that has to be got out of the way first. たあとで simply reports the order; てから implies the first event enables or licenses the second. The difference is small and native speakers often use either, but it shows up in a case like 大学だいがくを卒業そつぎょうしてから働はたらき始はじめた, which is natural, against the flatter 卒業そつぎょうした後あとで.

The second job has no equivalent in たあとで at all: てから plus a length of time plus になる measures how long it has been since something happened.

日本にほんに来きてから三年さんねんになります nihon ni kite kara sannen ni narimasu it's been three years since I came to Japan

Example. You arrived in Japan on 1 April 2019 and are speaking on 20 August 2026. What do you say?

Count the elapsed time first, because the sentence needs a number. From 1 April 2019 to 1 April 2026 is seven years; from there to 20 August 2026 is four months and nineteen days, so the total is seven years and four months, or 2698 days. Japanese rounds this the way English does, and you say 日本にほんに来きてから七年ななねんになります. If you want to be exact, 七年ななねん四よんか月げつになります. Note that the verb is 来きて, the て form of 来くる, and that になります rather than です is what makes it a duration reached rather than a fact stated.

Now you. You started studying Japanese in September 2021 and are speaking in August 2026. Say how long it has been, and say the same thing using 間あいだ instead.

ながら, and the rule about subjects

ながら joins two things happening at once. It attaches to the ます stem, the part left when ます comes off, so 聞ききます gives 聞ききながら and 食たべます gives 食たべながら.

音楽おんがくを聞ききながら勉強べんきょうする ongaku o kikinagara benkyou suru I study while listening to music

Two restrictions make ながら narrower than English "while", and both are absolute. First, both actions must have the same subject. You cannot say "while my brother watched television, I studied" with ながら; that needs 間あいだ, below. Second, the ながら clause is the background and the main clause is the point. The sentence above is about studying, with music in the background. Reverse them and 勉強べんきょうしながら音楽おんがくを聞きく is about listening to music, which is a different claim about how you spent the evening.

There is also a concessive ながら, used with states rather than actions, which means "although": 知しっていながら教おしえてくれなかった, they knew and still didn't tell me. It is much less common and belongs with the contrast patterns of the next lesson, but it is worth recognising so that you do not read it as simultaneity.

うちに, あいだ and あいだに

These three all cover a stretch of time, and the differences between them are sharp enough to be worth getting right.

あいだ is the whole stretch, and the main clause fills all of it.

夏休なつやすみの間あいだ、ずっと働はたらいていた natsuyasumi no aida, zutto hataraite ita I worked right through the summer holiday

あいだに adds に, which as always pins things to a point, so the main clause happens at some moment inside the stretch rather than across the whole of it.

夏休なつやすみの間あいだに旅行りょこうに行いった natsuyasumi no aida ni ryokou ni itta I went on a trip at some point during the summer holiday

That is a single kana carrying the entire difference between forty days of work and one trip inside forty days, which is a good illustration of how much load Japanese particles take. Note also that あいだ is free of the same-subject rule, so 兄あにがテレビを見みている間あいだに勉強べんきょうした is fine where ながら was not.

うちに also means "while", but it carries an implication that あいだに does not: the state described will not last, so act now.

熱あついうちに食たべてください atsui uchi ni tabete kudasai eat it while it's hot

若わかいうちにいろいろな国くにに行いきたい wakai uchi ni iroiro na kuni ni ikitai I want to visit lots of countries while I'm young

The negative version is where うちに earns its place, because あいだに cannot do it at all: 忘わすれないうちに書かいておきます, I'll write it down before I forget. Literally "while I have not yet forgotten", it is the ordinary way to say "before I forget", and it is far commoner than 忘わすれる前まえに.

Example. Which of 間あいだ, 間あいだに and うちに fits: 雨あめが降ふらない＿帰かえりましょう?

うちに. The sentence means "let's go home before it starts raining", and the three tests all point the same way: the clause is negative, describing a state that is expected to end; the main clause is a single event rather than something filling the whole period; and there is an implied urgency. 降ふらない間あいだに is not impossible but sounds like a neutral report of scheduling, and 降ふらない間あいだ would mean you stay home for the entire dry period, which is not what anyone means.

Now you. Choose between 間あいだ and 間あいだに, and explain: 先生せんせいが話はなしている＿、みんな静しずかに聞きいていた.

Vocabulary

Events can now be placed against each other in time. What they still cannot do is explain each other: nothing so far says that one thing happened because another did, or despite it. That pair of moves is what turns a run of sentences into an argument, and it is next.