でしょう / だろう: Probability & Confirmation | Japanese Grammar

でしょう and its plain-form twin だろう are the copula's conjectural forms — the shapes です and だ take when you are not stating a fact but making an educated guess about one. They do two jobs that English keeps separate but Japanese folds into a single word: they express probability ("it will probably rain") and, when spoken with rising intonation, they seek agreement ("nice, isn't it?"). The trick — and the thing textbooks structurally cannot teach on paper — is that intonation alone decides which of the two you mean.

The two jobs of でしょう

Job 1 — Probability (falling intonation)

With a falling tone, でしょう / だろう downgrades a statement from "this is so" to "this is probably so." It is the everyday tool of weather forecasts, cautious predictions, and any claim you can't fully vouch for.

明日は雨でしょう。

Ashita wa ame deshō

It will probably rain tomorrow.

北の地方では、夜から雪が降るでしょう。

Kita no chihō de wa, yoru kara yuki ga furu deshō

In the northern regions, it will (likely) snow from the evening.

This forecasting voice is why でしょう is the polite backbone of the weather report and of hedged assertions in service settings — it lets a speaker commit to a prediction without claiming certainty.

Job 2 — Confirmation (rising intonation)

With a rising tone, the same でしょう turns outward and asks the listener to agree: "…right?" You are not guessing — you are fairly sure, and you invite the other person to nod along.

この服、いいでしょう？

Kono fuku, ii deshō?

This outfit's nice, isn't it?

明日のパーティー、来るでしょう？

Ashita no pātī, kuru deshō?

You're coming to the party tomorrow, right?

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The falling でしょう means "I conjecture"; the rising でしょう？ means "don't you agree?" Nothing in the grammar or spelling distinguishes them — only the pitch contour does. This is a genuine case where prosody carries the meaning, so train your ear with real audio. See Intonation in Questions.

What でしょう attaches to

Unlike です, which follows nouns and な-adjectives, でしょう / だろう attaches to almost everything — nouns, both kinds of adjective, and the plain form of verbs — and it does so without だ.

Preceding word	Form	Example
Noun	noun + でしょう	学生でしょう (gakusei deshō)
な-adjective	stem + でしょう	元気でしょう (genki deshō)
い-adjective	plain + でしょう	高いでしょう (takai deshō)
Verb	plain + でしょう	行くでしょう (iku deshō)
Past	plain past + でしょう	難しかったでしょう (muzukashikatta deshō)

試験は難しかったでしょう。

Shiken wa muzukashikatta deshō

The exam was probably hard, wasn't it.

たぶん、思ったより高いでしょうね。

Tabun, omotta yori takai deshō ne

It's probably more expensive than you'd think.

Note that adverbs of probability like たぶん ("probably") and きっと ("surely") pair naturally with でしょう to fine-tune how confident the guess is — see The Probability Spectrum.

だろう: the plain form and its edge

だろう is simply the plain-style version of でしょう — same two jobs, but for casual speech, inner monologue, and writing. In its falling, musing use it voices a thought to yourself:

彼はもう帰っただろう。

Kare wa mō kaetta darō

He's probably already gone home.

彼女は元気だろうか。

Kanojo wa genki darō ka

I wonder if she's doing okay.

The pattern だろうか / でしょうか adds か to turn the conjecture into a genuine, hesitant wondering — "I wonder whether…" — softer and more thoughtful than a plain question.

But だろう carries a social edge that でしょう does not. Pointed at a listener, plain だろう can sound blunt, assertive, and stereotypically masculine — a "you already know this" tone.

そんなこと、言われなくても分かるだろう。

Sonna koto, iwarenakute mo wakaru darō

I know that without being told.

That sentence is fine between close friends but would sound harsh to a stranger or a superior. In polite conversation, use でしょう.

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だろう is not just "casual でしょう." Aimed at another person it can read as curt or challenging. When you are being polite — with customers, teachers, colleagues you don't know well — stay with でしょう even in otherwise plain-ish speech, and reserve だろう for talking to yourself or to close friends.

The service and forecasting register

Because でしょう lets a speaker predict or assert without full commitment, it is a workhorse of polite, hedged language. Forecasters, salespeople, and customer-service staff lean on it constantly, often combined with the explanatory んです as んでしょう, or with the ultra-polite でしょうか.

あなたも行くんでしょう？

Anata mo iku n deshō?

You're going too, aren't you?

お待たせしました。こちらでよろしいでしょうか。

Omatase shimashita. Kochira de yoroshii deshō ka

Sorry to keep you waiting. Would this be all right?

でしょうか is markedly gentler than ですか: instead of demanding a fact, it floats the question as a possibility, giving the listener room to decline.

でしょう vs. と思います: guessing about the world vs. holding an opinion

English speakers often reach for と思います ("I think") where a native would use でしょう, and vice versa. The two are not interchangeable. でしょう makes a guess about how the world is — it points outward at a fact you can't confirm. と思います attributes a personal opinion or judgment to yourself — it points inward at what you believe.

明日は晴れるでしょう。

Ashita wa hareru deshō

It'll probably be sunny tomorrow. (a forecast about the world)

この映画は面白いと思います。

Kono eiga wa omoshiroi to omoimasu

I think this movie is interesting. (my personal take)

The forecaster says 晴れるでしょう because sunshine is a fact of the world she is predicting; she would not say 晴れると思います on air, because that would reduce a professional forecast to a private hunch. Conversely, offering your opinion of a film with 面白いでしょう would sound like you're guessing at a fact rather than sharing what you think — unless you tack on the rising tone to mean "it's interesting, don't you agree?"

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Rule of thumb: if you could paraphrase your sentence as "it is probably the case that…", use でしょう. If you'd paraphrase it as "in my view / I reckon…", use と思います. Forecasts, deductions, and hedged facts take でしょう; evaluations, preferences, and beliefs take と思います.

Common Mistakes

Mistake 1: Reading every でしょう as a question. A falling でしょう is a statement of probability, not a question. 明日は雨でしょう means "it'll probably rain," full stop — it is not asking anything. Only the rising でしょう？ requests confirmation. Getting the intonation wrong flips your meaning entirely.

Mistake 2: Inserting だ before でしょう. Nouns and な-adjectives attach directly.

❌ 彼は学生だでしょう。

Incorrect — no だ before でしょう.

✅ 彼は学生でしょう。

Kare wa gakusei deshō

He's probably a student.

Mistake 3: Using だろう where politeness is required.

❌ 先生も参加するだろう？

Too blunt/familiar toward a teacher.

✅ 先生も参加なさるでしょう？

Sensei mo sanka nasaru deshō?

You'll be taking part too, won't you, sensei?

Mistake 4: Conjecturing about your own decided actions. でしょう / だろう expresses a guess about something outside your control or knowledge. Don't use it for a firm decision you yourself have made.

❌ 私は明日、会社を休むでしょう。

Odd — you don't guess about your own settled plan.

✅ 私は明日、会社を休みます。

Watashi wa ashita, kaisha o yasumimasu

I'm taking tomorrow off work.

If the plan is genuinely yours and decided, use the plain future/non-past (休みます). Save でしょう for what you can only guess at.

Key Takeaways

でしょう (polite) and だろう (plain) are the copula's conjectural forms and do two jobs at once.
Falling tone = probability ("probably"); rising tone = confirmation ("right?"). Intonation, not grammar, tells them apart.
They attach directly — with no だ — to nouns, adjectives, and plain-form verbs, past or non-past.
だろう can sound blunt or masculine when aimed at a listener; prefer でしょう when being polite.
でしょうか / だろうか adds hesitant "I wonder…" softness, the backbone of polite service and forecasting speech.

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