とwhen, whenever; if (it always follows)
と is for what follows by itself: press this and that happens, spring comes and the days get longer. English says "when", "whenever" or "if".
how it works
When you press this button, the screen becomes brighter.
every year
When spring comes, the days get longer.
a habit
Whenever Kenta gets home, he washes his hands first.
Verb
dictionary form／ない-form + と
押すと, 押さないと. Never the た-form, even in a sentence about the past.
い-adjective
adjective + と
寒いと, 寒くないと
な-adjective, noun
な-adjective／noun + だ + と
静かだと, 雨だと. The だ stays. 雨と with no だ is the other と, "rain and…".
What always follows
Mostly と is about what happens every time. Directions use it too.
Turn right at the corner, and you'll find a post office.
When the weather is bad, you can't see the mountains from here.
If it rains, the game is called off.
と or たら?
A request, an invitation or a plan never follows と. What you ask, suggest or plan takes たら.
When spring comes, the cherry blossoms bloom.
Every year. Nobody decides it.
When spring comes, let's go and see the cherry blossoms.
This spring, and an invitation.
Not said: 駅に
(Please call when you arrive at the station.)
と is for what follows by itself. A request doesn't.
Please call when you arrive at the station.
First you arrive, then you call, this once. たら takes the request.
Warnings
A warning is the same と: carry on like this, and here is what follows. With ないと it is "if you don't".
If you eat that much, you'll get a stomachache.
If you don't hurry, you won't make it.
After a noun, がないと with a "can't" after it is the everyday "can't … without": "if there is no…". About a person it is がいないと.
You can't board a plane without a passport.
You can't get by in this town without a car.
In a story: what happened next
Telling a story, と links what someone did to what came next, usually something they found. The verb before と still takes no た. In conversation people more often say this with たら.
When I opened the window, there was a white cat in the garden.
The four ways to say "if"
Often more than one would fit, but each has its own job. One heater, four sentences, と first.
When you press this switch, the heating comes on.
たらN4
The everyday "if" and "when": one thing happens, then the other. Of the four, the safe choice when you are not sure.
If it is cold, please turn on the heating.
ばN4
For what a result depends on: the "if" of advice and instructions. After something you do, a request takes たら, not ば.
You can turn on the heating if you press this button.
ならN4
Takes up what was just said or supposed, and answers it. Nothing has to happen first, so the answer is often advice about what to do beforehand.
If you are going to use the heating, please close the window first.
Close neighbours
とN5
A different と: "and", "with", and the mark of what was said or thought.
My older brother and older sister came.
ないとN4
The warning with its second half left unsaid: "I have to".
The train is about to leave. I have to go.
と～た・たら～たN3
The story use in full, with たら beside it.
When I woke up in the morning, everything outside was covered in snow.
Check yourself
1Which one fits?
家に
Choose an answer to see why.
2Which one fits?
ドアを
Choose an answer to see why.
More detail
ですと in shops and offices
Staff speaking to a customer often make the first half polite as well, with ですと.
For students, the admission fee is half price.
More sentences
Pulling this lever makes the seat recline.
When the temperature falls to zero or below, water freezes.
When summer comes, more tourists visit this lake.
Whenever my grandmother looked at old photos, she would always tell the same story.