たらif; when, once
たら is the everyday "if" and "when": one thing happens, then the other. Which word English uses depends on how sure the first thing is.
if
If it is sunny tomorrow, would you like to have lunch in the park?
when, once
Please call when you arrive at the station.
when I did, I found
When I woke up in the morning, everything outside was white.
Verb
行った → 行ったら 飲んだ → 飲んだら した → したら
The plain past, the た-form, with ら added. The half before たら is normally plain, even when the sentence ends in ます or ください.
い-adjective
寒かった → 寒かったら
いい becomes よかったら.
な-adjective, noun
静かだった → 静かだったら 雨だった → 雨だったら
Negative
行かなかった → 行かなかったら 寒くなかった → 寒くなかったら
If, when, once
If it rains, I'll go by taxi.
It may not rain: "if".
Let's leave once the rain stops.
It will stop sooner or later: "when", "once".
もし at the front makes it clearly "if": もし雨が降ったら. It is optional.
If you don't know the way, please ask the station staff.
If it's expensive, I won't buy it this time.
If you are free, please give me a hand.
Once work is over, let's meet at the station.
The た doesn't make the sentence past. It says the first half is done before the second begins, so a sentence about tomorrow takes it too.
If I don't get a reply by tomorrow, I'll call you.
Looking back: when I did, I found
About the past, たら tells what you found, or what happened, when you did something.
When I opened the box, I found an old letter inside.
When I took the medicine, my fever went down.
What can't follow たら here is the next thing you chose to do. English "when I got home, I took a shower" is two things you did, and Japanese says that with the て-form.
When I got home, a letter had come.
What you found.
Not said: 家に
(When I got home, I took a shower.)
What you did next: not with たら.
When I got home, I took a shower.
たら、すぐ: as soon as
すぐ, "right away", makes it "as soon as": たら、すぐ for what you ask or plan, and the て-form with すぐ for the next thing you did.
Please call as soon as you arrive at the station.
I called my mother as soon as I got to the station.
Things people say
よかったらif you like
If you like, why don't we go together?
〜たら？why don't you…?
Why don't you rest for a bit?
A suggestion between friends.
The four ways to say "if"
Often more than one would fit, but each has its own job. One heater, four sentences, たら first.
If it is cold, please turn on the heating.
とN4
For what follows by itself: how machines work, what the seasons bring, habits, directions. Never followed by a request, an invitation or a plan.
When you press this switch, the heating comes on.
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.
Only たら can say this
駅に着いたら、電話してください is a request, for one occasion, after something you do. Of the four, only たら can say it. That is why it is the safe choice when you are not sure.
Not said: 駅に
(Please call when you arrive at the station.)
と is for what follows by itself. A request doesn't.
Not said: 駅に
(Please call when you arrive at the station.)
Arriving is something you do, and after an action ば leads to a result.
Not said: 駅に
(Please call when you arrive at the station.)
This says "if you are going to arrive", as if the call came first.
Close neighbours
ときN5
"When" as a time: a time of life, a kind of occasion. For one thing that will follow another, "when" is usually たら.
When I was a child, I lived in Kyoto.
てからN5
"After doing": the order and nothing more. About the past, it is fine for two things you did.
I bought a ticket at the station and then boarded the train.
と～た・たら～たN3
Looking back, in full: the things people say with it, like てみたら, "when I tried it", and と, which stories use for the same thing.
When I tried it, it was better than I expected.
The suggestion in full: "why don't you…?", "how about…?"
You don't look well. Why don't you go home early today?
Asking what to do. どうしたら and どうすれば mean the same here.
My computer suddenly stopped working. What should I do?
"If I had…, I would…" is the same たら. のに at the end adds that it isn't so, and that you are sorry.
If I had the money, I'd buy a new car.
How the plain past, the た-form, is made.
I drank coffee yesterday.
Check yourself
1Which one fits?
春に
Choose an answer to see why.
2Which sentence sounds natural?
Choose an answer to see why.
3What does this mean?
大人に
Choose an answer to see why.
More detail
ましたら
Staff speaking to a customer often make the first half polite as well, with ましたら.
I will call you when it is ready.
More sentences
If it rains tomorrow, the game will probably be canceled.
If you have time, please take these documents to the post office on your way back.
If the weather is good this weekend, would you like to go to the beach?
Once you have checked the documents, please submit them at reception.
When I went into the café, an old friend was sitting by the window.
When I got back to the room, there was a small box on the desk.