Saying how sure you are: "probably", "should be", "must be"
When you say something you haven't checked, the end of the sentence shows how sure you are: "probably", "should be", "must be". It also shows what you have to go on, such as a schedule or a clue in front of you. In conversation the ending to start with is と思う, "I think".
| Form | What it says | Where |
|---|---|---|
| と思う | "I think": a guess or an opinion, offered as your own view | Everyday |
| でしょう, だろう | "Probably": a guess about what you can't know for sure | Weather forecasts, formal speech; だろう in writing |
| はずだ | "Should be": you expect it, from a schedule or a promise | Everyday |
| に違いない | "Must be": you are convinced, usually by a clue in front of you | Novels, essays, columns |
| に相違ない | The same as に | Legal papers, older novels |
| に決まっている | "Of course": you are sure, and say so flatly | Conversation, arguments, dramas |
と思う: I think
Full pageと思うN4
と思う is how people usually give a guess in conversation. With たぶん it is "probably", and with きっと, "I'm sure".
I think the trains will be crowded tomorrow.
I don't think he'll come.
English says "I don't think". Japanese usually says "I think he won't".
でしょう・だろう: probably
Full pageでしょう・
With a falling voice, でしょう is "probably"; with a rising one it is "right?". だろう is the plain form, for what you think to yourself or write. Said aloud with nothing after it, it is blunt, and mostly men say it.
Tomorrow it will probably start raining in the afternoon.
The lights are on, so Tanaka is probably still at the office.
Tanaka will probably come.
Sure of itself. In conversation it can sound like a forecaster or a teacher.
I think Tanaka will probably come.
How people usually give a guess.
はずだ: should be
Full pageはずだ・
はずだ is "should" in the sense of "I expect so": you haven't checked, but a schedule, a promise or something you know tells you so.
According to the schedule, the train should arrive at ten.
He should be at the station by now, but I still haven't heard from him.
はずなのに is "it should, and yet…".
Is Tanaka in?
No, he should be off today.
The honest answer when you believe something but can't promise it.
はずがない is "it can't be": from what you know, there is no way.
This bag is empty, so it can't be heavy.
Where it goes wrong
English "should" also gives advice. はずだ doesn't: it says what you expect to be true.
You practice every day, so you should get better.
What you expect to happen.
You should practice every day.
Advice. That is たほうがいい.
Neither でしょう nor はずだ is for your own plans. A plan is decided, not guessed or expected.
Sounds odd: 私は
I will probably go to Kyoto tomorrow.
For a plan, 行きます; if you aren't sure, たぶん行くと思います.
に違いない: must be
Full pageに違いない・
に違いない is the "must" of being convinced, never the "must" of "have to".
The lights are off and there is no answer. They must have gone to bed already.
Said to a friend, it sounds like a line from a novel. People say きっと…と思う instead, or 絶対…だよ when they are surer still.
After all that practice, she is sure to be fine on the day too.
Written, or thought to yourself.
After all that practice, I'm sure she'll be fine on the day too.
To a friend.
After all that practice, she'll definitely be fine on the day too.
To a friend, and surer still.
に相違ない says the same in stiff writing.
With so much of the testimony in agreement, there can be no doubt that he knew the facts.
だろう, はずだ or に違いない?
All three say that a shop is closed. What differs is how sure you are, and what you go on.
Since it is Sunday, this shop is probably closed.
A guess: you suppose it closes on Sundays.
It's Sunday today, so that shop shouldn't be open.
As far as you know, it does close on Sundays. You haven't been to look.
The shop's shutters are down. It must be closed today.
A clue in front of you, and you are convinced.
に決まっている: of course
Full pageに決まっているN2
に決まっている is "of course" or "it has to be", said as if nobody could think otherwise. It is at least as sure as に違いない, but spoken, and often impatient. In conversation it becomes に決まってる.
Oh, come on. That's obviously a lie.
It's snowing outside, so of course it's cold.
に違いない or に決まっている?
Both are sure that the rent is high.
This close to the station, the rent must be high.
Reasoned out from how close it is.
The shop is right by the station, so of course the rent is high.
Said flatly: what else could it be?
After a noun
Not every ending joins a noun such as 休み, "closed", in the same way.
| Ending | After a noun |
|---|---|
| と思う | 休みだと |
| でしょう | 休みでしょう |
| はずだ | 休みのは |
| に違いない | 休みに |
| に決まっている | 休みに |
A な-adjective joins as the noun does, with one exception: 静かなはずだ.
Other things "should", "must" and "of course" can mean
ばよかったN4
The "should have" of regret: you didn't, and wish you had.
Oh, rain. I should have brought an umbrella.
もちろんN3
The "of course" that says yes to a request.
Of course. We're friends, so naturally I will.
It answers 明日の引っ越し、手伝ってくれる？, "Can you help me move tomorrow?" 当然 is "naturally".
Less sure than "probably"
A conclusion, not a guess
わけだN3
"No wonder": you hear the reason for something you had noticed. Or "which means": you work out what the facts come to.
Oh, today is a public holiday. So that's why the bank is closed.