If and when with と

～と ~to If/when; natural consequence

After a verb, と means "if" or "whenever": the result always follows. Press the button and hot water comes out.

Level: JLPT N5, beginner
Type: Linking ideas
English links: zero conditional, first conditional, if and when

What it means

You know と as "and" or "with" between nouns. After a verb in the dictionary form, it means something else: if, or whenever. 春になると、桜が咲きます. When spring comes, the cherry trees bloom.

This と is for results that follow every time, or as a matter of course. Machines, nature, directions and habits all fit. このボタンを押すと、お湯が出ます. Press this button and hot water comes out.

The second half cannot be a request, an invitation or your own plan. You cannot say 駅に着くと、電話してください. For that, Japanese uses たら, which you will meet at N4. So と sentences describe how the world works. They do not ask anyone to do anything.

How to build it

Pattern	How it works
Dictionary form + と、result dictionary form + to, result	押す → 押すと. If you press, then...
ない form + と、result nai form + to, result	寝ない → 寝ないと. If you don't sleep, then...
い-adjective + と / noun + だと i-adjective + to / noun + da to	寒いと, 雨だと. If it is cold, if it is rain.

Examples

春になると、桜が咲きます。 haru ni naru to, sakura ga sakimasu. When spring comes, the cherry trees bloom.
このボタンを押すと、お湯が出ます。 kono botan o osu to, oyu ga demasu. If you press this button, hot water comes out.
右に曲がると、駅があります。 migi ni magaru to, eki ga arimasu. Turn right and you'll see the station.
雨が降ると、電車が遅れます。 ame ga furu to, densha ga okuremasu. When it rains, the trains are late.
寝ないと、次の日眠いです。 nenai to, tsugi no hi nemui desu. If I don't sleep, I'm tired the next day.

How English says it

English splits this into "if" and "when". "When" is for things that will surely happen: when spring comes. "If" is for things that may or may not happen: if you press the button. Japanese と covers both.

For general truths, English uses the zero conditional: if or when + present, then present. "If you heat ice, it melts." For one future event, it uses the first conditional: "If you turn right, you'll see the station." English can also use an order and "and": "Turn right and you'll see it."

Why it can make English hard

と covers both "if" and "when", so many students pick one and use it for everything. "If spring comes" sounds as if spring might not come.
Japanese has no future form in the if part. Some learners still put "will" there in English, which English does not allow: "If it will rain".
Students know と as "and", so a few translate the condition as "and" in odd places, or leave the link out.

Mistakes you will hear

If spring comes, cherry blossoms bloom. When spring comes, the cherry trees bloom. Spring comes every year, so English uses "when".
If you will press this button, hot water comes out. If you press this button, hot water comes out. No "will" after "if" in a condition.
If it rain, train is late. If it rains, the trains are late. Third-person -s on "rains", and the noun needs an article or a plural.

In the classroom

Bring a vending machine or a microwave into the lesson, or a picture of one. Students explain it: "If you press this, coffee comes out." Real machines make the zero conditional stick.
Read sentences aloud and ask "Sure or maybe?" Sure gets "when", maybe gets "if". It takes five minutes and clears up a common mix-up.
Give directions on a school map: "Go straight and you'll see the gym. If you turn left, you'll find the library."

Practice

Try each one, then open it to check.

1. Fill the gap: 冬になる＿、寒くなります。 (When winter comes, it gets cold.)

Answer: と

A natural result that follows every time takes と.
2. Translate: このボタンを押すと、ドアが開きます。

Answer: If you press this button, the door opens.

A machine always does the same thing, so English uses the zero conditional.
3. A student writes "If summer will come, I go to the sea." Fix it.

Answer: When summer comes, I go to the sea.

Summer always comes, so use "when", and no "will" in that part.
4. Is this natural Japanese? 駅に着くと、電話してください。

Answer: No. Use 駅に着いたら、電話してください。

A request cannot follow と. たら (N4) is the form for that.