Learn Hardcore Japanese: gakkou ni iku toki, eki de koohii wo kaimasu. - When I go to school, I buy coffee at the station.

In Japanese, に marks the destination with movement verbs like 行く. It means “to school.” You could also use へ for direction, but に emphasizes the specific endpoint.

Why is 行く in its dictionary form instead of 行きます?

When a verb precedes とき (“when”), you use the plain (dictionary) form in that subordinate time clause. That’s why it’s 学校に行くとき. The main clause can still use polite form (買います).

What does とき mean and how does it function here?

とき means “time” or “when.” It attaches to a verb or phrase to create a time expression. So 学校に行くとき means “when (I) go to school.” It links this time clause to the main action.

Why is there a comma after とき?

The comma separates the subordinate time clause (学校に行くとき) from the main clause (駅でコーヒーを買います). It’s optional in Japanese but makes the sentence easier to read.

Why is 駅 followed by で?

The particle で marks the location where an action occurs. 駅で means “at the station,” showing where you buy coffee.

Why is コーヒー marked by を?

を is the direct-object marker. コーヒーを買います literally means “(I) buy coffee.”

Who is the subject of this sentence? There’s no 私 or 僕.

Japanese often omits the subject when it’s clear. Here, it’s understood as “I.” If you need to clarify, you can add 私は at the start.

What’s the difference between 学校に行くとき and 学校に行く前に?

学校に行くとき means “when I go to school” (at the moment of going).
学校に行く前に means “before I go to school” (some time prior).

Can I say 学校に行くときに? Why is the second に often omitted?

You can say 学校に行くときに駅で…, but it’s common to drop the second に because 学校に行くとき already functions as an adverbial time phrase. Omitting the extra に sounds more natural.

What if I use 行ったとき (past plain) instead of 行くとき?

Using 行ったとき means “when I have gone” or “after I went.” So 学校に行ったとき、駅でコーヒーを買います would imply you buy coffee after arriving at school, which doesn’t match the intended meaning. Use 行くとき for actions coinciding with departure.