toki-vs-mae-ni-vs-ato-de

2026年4月27日

You’re telling your friend about your daily routine in Japanese. You know you want to say “before I eat breakfast” and “when I get home” — but which grammar pattern do you reach for? Japanese has three essential time expressions that English speakers constantly mix up: とき (toki), 前に (mae ni), and 後で (ato de). Each one does something different, and — here is the twist — the verb form that comes before them can change the entire meaning of your sentence. This guide will make all three click for you once and for all.

Expression	Meaning	Verb form before it	Example
とき	when / at the time of	Dictionary form (ongoing) or た-form (completed)	食べるとき / 食べたとき
前に	before doing X	Always dictionary form	食べる前に
後で	after doing X	Always た-form	食べた後で

TOC

とき — “When”: The Expression with a Hidden Tense Rule

とき (toki) means “when” or “at the time of.” It connects two events by pointing to the moment one action takes place. So far, so easy. The tricky part is what happens to the verb that comes right before とき — and this is where most learners make mistakes.

The rule depends on whether the first action is still in progress or already completed when the second action occurs.

Dictionary form + とき = the action is not yet done

Use the plain (dictionary) form of the verb before とき when the first action has not yet been completed at the time of the second action. Think of it as “at the point in time when I am about to / in the process of doing X.”

Japanese	English
日本に行くとき、ガイドブックを買った。	When I went to Japan (before I left / while en route), I bought a guidebook.
家を出るとき、鍵を確認してください。	When you leave the house (as you are leaving), please check your keys.
日本語を勉強するとき、単語帳を使います。	When I study Japanese, I use a vocabulary notebook.

Notice the guidebook example: the speaker bought the book before arriving in Japan — so the act of “going” was not yet complete. The dictionary form captures that “before completion” timing.

た-form + とき = the action is already done

Use the past (た) form of the verb before とき when the first action is already completed when the second action happens. Think of it as “at the point in time after X was done.”

Japanese	English
日本に着いたとき、友達が迎えに来てくれた。	When I arrived in Japan (after arriving), my friend came to pick me up.
宿題が終わったとき、もうお腹が空いていた。	When my homework was finished, I was already hungry.
子どもの頃、転んだとき、いつも泣いていた。	When I was a child, whenever I fell, I always cried.

Yuka

So to summarize とき: ask yourself, “Is the first action done yet when the second action happens?” Not done yet = dictionary form. Already done = た-form. That one question is the whole rule!

前に — “Before”: Always Dictionary Form, No Exceptions

前に (mae ni) means “before doing X.” It tells us that the second action happens prior to the first action. The grammar structure is simple:

[Verb dictionary form] + 前に + [main action]

The critical rule: the verb before 前に is ALWAYS in dictionary (plain non-past) form, even when the sentence is in the past tense overall. This is a fixed rule with no exceptions for verb-based 前に clauses.

Japanese	English
寝る前に、歯を磨きます。	Before sleeping, I brush my teeth.
日本に来る前に、ひらがなを覚えました。	Before coming to Japan, I learned hiragana.
食べる前に手を洗ってください。	Before eating, please wash your hands.
映画が始まる前に、ポップコーンを買おう。	Before the movie starts, let’s buy popcorn.

Notice the second example: the sentence is in the past tense (“I learned”), but the verb before 前に stays as 来る, not 来た. This surprises many English speakers who want to match tenses. In Japanese, 前に locks in the dictionary form regardless of when the sentence took place.

Nouns with 前に: When using a noun (not a verb), you attach の before 前に:

Structure	Example	English
[Noun] + の前に	食事の前に	Before the meal
[Noun] + の前に	授業の前に	Before class

Rei

I used to write 食べた前に and wonder why it sounded wrong. The answer: 前に never takes the た-form before it. Dictionary form only — always.

後で — “After”: Always た-form, Plus the てから Alternative

後で (ato de) means “after doing X.” It tells us that the main action happens following the completion of the first action. The structure is:

[Verb た-form] + 後で + [main action]

The rule here is the mirror image of 前に: the verb before 後で is ALWAYS in た-form. This makes intuitive sense — you can only do something “after” a completed action, so the past form fits.

Japanese	English
宿題をした後で、ゲームをします。	After doing homework, I play games.
シャワーを浴びた後で、寝ました。	After taking a shower, I went to sleep.
考えた後で、返事をします。	After thinking about it, I will reply.
日本語を勉強した後で、アニメが分かるようになった。	After studying Japanese, I became able to understand anime.

てから: A closer alternative to 後で

Japanese offers another “after” expression: [Verb て-form] + から. This is often interchangeable with 後で, but with a subtle difference:

Pattern	Nuance	Example
[た-form] + 後で	Neutral “after X, Y happened” — the two events can be loosely related in time	食べた後で、散歩した。
[て-form] + から	Stronger sequence — Y happens directly as a result or next step after X	食べてから、散歩した。

In everyday conversation, the difference is small and both are widely used. However, てから sounds more like a deliberate sequence (“first X, then immediately Y”), while 後で can allow more time between the events.

Nouns with 後で:

Structure	Example	English
[Noun] + の後で	授業の後で	After class
[Noun] + の後で	仕事の後で	After work

Side-by-Side: The Same Situation, Three Ways

The best way to see the difference is to express the same real-life scenario using all three patterns. Let’s use the situation: eating dinner and taking a bath.

Expression	Japanese	English gloss	Key focus
とき (ongoing)	ご飯を食べるとき、テレビを見ます。	When I eat dinner, I watch TV.	Simultaneous or habitual — both happening together
とき (completed)	ご飯を食べたとき、電話が鳴った。	When I had finished eating, the phone rang.	First action done; second action happened right then
前に	お風呂に入る前に、ご飯を食べます。	Before taking a bath, I eat dinner.	Eating happens first — defines the order
後で	ご飯を食べた後で、お風呂に入ります。	After eating dinner, I take a bath.	Eating is done; bath comes next

Notice how 前に and 後で are essentially mirror images of each other in the last two rows — they describe the same reality from opposite directions. And とき is different from both: it locates a moment in time rather than establishing a before-or-after sequence.

Yuka

I find it helpful to think of 前に and 後で as bookends. 前に puts event A before the bookend, 後で puts it after. とき is completely different — it is a spotlight on a specific moment, not a sequence marker.

The Classic Mistake: Wrong Verb Form Before とき

The number one error learners make is using the wrong verb form before とき. Because the tense rule of とき is unique to Japanese (English “when” does not require this distinction), English speakers often guess wrong or use the wrong form by habit.

Mistake 1: Using た-form when dictionary form is needed

Wrong	Correct	Why
❌ 日本に行ったとき、ガイドブックを買った。	✅ 日本に行くとき、ガイドブックを買った。	The guidebook was bought before arriving — the “going” action was not yet complete
❌ 家を出たとき、鍵を確認してください。	✅ 家を出るとき、鍵を確認してください。	Checking keys happens as you leave — not after you have already left

Mistake 2: Using dictionary form when た-form is needed

Wrong	Correct	Why
❌ 日本に着くとき、友達が迎えに来てくれた。	✅ 日本に着いたとき、友達が迎えに来てくれた。	The friend arrived after the speaker had already landed — arrival is complete

Mistake 3: Using た-form before 前に

Wrong	Correct	Why
❌ 寝た前に、歯を磨きます。	✅ 寝る前に、歯を磨きます。	前に always requires dictionary form before it — no exceptions

Mistake 4: Using dictionary form before 後で

Wrong	Correct	Why
❌ 宿題をする後で、ゲームをします。	✅ 宿題をした後で、ゲームをします。	後で always requires た-form — the preceding action must be completed

Rei

The pattern I use to remember this: 前に is “not yet done” (dictionary form), 後で is “already done” (た-form), and とき can be either one depending on the situation. If you remember just that, you will catch 90% of errors.

Decision Flowchart: Which Expression Do I Use?

Use this flowchart whenever you are unsure which time expression to reach for:

Are you describing a sequence (one thing happens before/after another)?
|
+-- YES --> Is the main action happening BEFORE the other action?
|               |
|               +-- YES --> Use 前に
|               |           Verb before 前に: ALWAYS dictionary form
|               |           Example: 寝る前に歯を磨く
|               |
|               +-- NO  --> The main action happens AFTER the other action
|                           Use 後で (or てから for a tighter sequence)
|                           Verb before 後で: ALWAYS た-form
|                           Example: 宿題をした後でゲームをする
|
+-- NO --> Are you pointing to a specific moment or circumstance?
            Use とき ("when / at the time of")
            |
            +-- Is the first action COMPLETE when the second happens?
            |       YES --> た-form + とき
            |               Example: 日本に着いたとき、電話した
            |
            +-- Is the first action NOT YET COMPLETE (ongoing/habitual)?
                    YES --> dictionary form + とき
                            Example: 日本に行くとき、本を買った

Quick Quiz: Test Yourself

Fill in the blank with the correct expression or verb form. Answers are below each question.

Question 1: Choose とき, 前に, or 後で.
「シャワーを浴びた___、朝ご飯を食べます。」
(I eat breakfast after taking a shower.)

Answer 1: 後で → 「シャワーを浴びた後で、朝ご飯を食べます。」
The shower is already completed before breakfast — 後で is the right fit. The verb 浴びた is already in た-form, which is correct before 後で.

Question 2: Choose the correct verb form (行く or 行った).
「アメリカに___とき、お土産を買ってきてね。」
(When you go to America, please bring back a souvenir.)

Answer 2: 行く → 「アメリカに行くとき、お土産を買ってきてね。」
The souvenir is bought on the way — the trip is not yet completed when the buying happens. Dictionary form is correct.

Question 3: Correct the error in this sentence.
「映画を見た前に、ポップコーンを買った。」

Answer 3: 「映画を見る前に、ポップコーンを買った。」
前に requires dictionary form before it. 見た (past) must be changed to 見る (dictionary form).

Question 4: Choose とき, 前に, or 後で.
「子どもの___、よく公園で遊んでいた。」
(When I was a child, I often played in the park.)

Answer 4: とき → 「子どものとき、よく公園で遊んでいた。」
This sentence points to a time period (“when I was a child”), not a before/after sequence. とき is used here with a noun (子ども + の + とき).

Question 5: Choose the correct verb form (食べる or 食べた).
「ご飯を___後で、薬を飲んでください。」
(After eating, please take your medicine.)

Answer 5: 食べた → 「ご飯を食べた後で、薬を飲んでください。」
後で requires た-form. The meal must be completed before taking the medicine.

Question 6: Translate into Japanese using 前に.
“Before leaving the house, I always check my wallet.”

Answer 6: 「家を出る前に、いつも財布を確認します。」
出る (dictionary form) + 前に is the correct structure. Never 出た前に.

How did you do? If you missed any questions about verb form, go back and re-read the とき tense rule section — that is the most nuanced part of this grammar point.

Which of these three expressions do you find hardest to use naturally? Drop a comment below — your question might help other learners too!

Keep Learning

Now that you have mastered とき, 前に, and 後で, take your Japanese time expressions further with these related guides:

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