〜だろう

Probably ~ / ~, right? (casual)

だろう is the plain (casual) form of でしょう. It means "probably ~", and with a rising tone it checks that the listener agrees: "~, right?"

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How to make it

Rule	Example
Verb plain form + だろう	来る → 来るだろう／来ない → 来ないだろう
い-adjective + だろう	さむい → さむいだろう
Noun／な-adjective + だろう (no だ)	雨 → 雨だろう／しずか → しずかだろう
Plain past + だろう	行った → 行っただろう

Meaning and examples

1. Guessing: probably

Say what you think is likely, without being sure. It often comes with たぶん.
- あしたは雨がふるだろう。
  
  あしたはあめがふるだろう。
  
  ashita wa ame ga furu darou.
  
  It will probably rain tomorrow.
- たなかさんはもううちにかえっただろう。
  
  たなかさんはもううちにかえっただろう。
  
  tanaka san wa mou uchi ni kaetta darou.
  
  Tanaka has probably gone home already.
- とうきょうは今ごろさむいだろう。
  
  とうきょうはいまごろさむいだろう。
  
  toukyou wa imagoro samui darou.
  
  It's probably cold in Tokyo around now.
- かれはたぶん来ないだろう。
  
  かれはたぶんこないだろう。
  
  kare wa tabun konai darou.
  
  He probably won't come.
2. Checking: right?

With a rising tone, だろう？ asks the listener to agree with something you think they know.
- あしたのパーティー、行くだろう？
  
  あしたのパーティー、いくだろう？
  
  ashita no paatii, iku darou?
  
  You're going to tomorrow's party, right?
- ほら、言っただろう？
  
  ほら、いっただろう？
  
  hora, itta darou?
  
  See? I told you, didn't I?
3. Wondering to yourself

After a question word (だれ, 何, いくら), だろう means "I wonder ~" when you are thinking aloud.
- あの人はだれだろう。
  
  あのひとはだれだろう。
  
  ano hito wa dare darou.
  
  I wonder who that person is.
- このかばんはいくらだろう。
  
  このかばんはいくらだろう。
  
  kono kaban wa ikura darou.
  
  I wonder how much this bag is.

Nuance

だろう is casual. In conversation it sounds rather masculine or blunt, so it is mostly heard among friends, in thinking aloud, and in writing such as news or essays. When speaking politely, use でしょう instead. Never put だ before だろう: say 雨だろう, not 雨だだろう.

Compared with

〜でしょう

でしょう is the polite form with the same meanings. Use でしょう with teachers, strangers and in polite conversation.

〜と思います

と思います clearly gives your own opinion and is polite. だろう is a guess in plain style and sounds less personal.

Common mistakes

Wrongあしたは雨だだろう。

Rightあしたは雨だろう。

After a noun, だろう replaces だ, so you never say だだろう.

Wrongこのへやはしずかなだろう。

Rightこのへやはしずかだろう。

な-adjectives drop な before だろう.

Wrong先生、あしたは雨がふるだろう。

Right先生、あしたは雨がふるでしょう。

だろう is too casual for a teacher; use でしょう in polite speech.

Practice

JLPT style: choose the best answer for （　）.

1あしたはたぶん雨（　）。
2かれはたぶんパーティーに（　）だろう。
3たなかさんはもううちに（　）だろう。
4このへやはしずか（　）。

FAQ

What is the difference between だろう and でしょう?

They mean the same thing. でしょう is polite and safe in most situations; だろう is plain and used with friends, when thinking aloud, or in writing.

Is だろう rude?

It is not rude, but it is casual and can sound blunt or masculine in speech. Many speakers, especially women, prefer でしょ or other endings in casual talk, and everyone uses でしょう when being polite.

What does だろう？ with a rising tone mean?

It means "~, right?" and asks the listener to agree, as in 行くだろう？ (You're going, right?). It is very casual.

More in Sentence basics

〜は〜ですX is Y 〜は〜ですかIs X Y? (question)〜でしたWas / were (past polite)〜ねIsn't it? / Right? (seeking agreement)〜よI tell you / you know (assertion)〜じゃないです／〜ではありませんIs not ~ (negative)〜と思いますI think that ~〜んです／〜のですIt's that ~ (explanation / emphasis)〜でしょうProbably ~ / I suppose ~〜のですかIs it that ~? (seeking explanation)〜だ (plain copula)Is / am / are (casual)お〜／ご〜Polite prefix 〜なあExclamation / musing (casual)

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