だろう

Probably

Level 2Sounds Like darou

Meaning: Probably; I guess; I suppose.
Function: Expresses the speaker's conjecture or reasoning about a situation.
Politeness: Casual (the plain form of でしょう).

How It Works

1. Formation Rules
だろう attaches to the plain form of words in both present and past tenses:

  • Verbs: [Plain Form] + だろう (e.g., 行く + だろう / 行った + だろう)
  • い-Adjectives: [Plain Form] + だろう (e.g., 寒い + だろう / 寒かった + だろう)
  • な-Adjectives: [Stem] + だろう (e.g., 元気 + だろう / 元気だった + だろう) — Note: In the present tense, do not use だ.
  • Nouns: [Noun] + だろう (e.g., 雨 + だろう / 雨だった + だろう) — Note: In the present tense, do not use だ.

2. Nuance and Certainty
While often translated as 'maybe,' だろう implies a high level of confidence (around 70-80%). The speaker usually has a logical basis for their guess. In casual speech, it is frequently shortened to だろ.

3. Seeking Confirmation and 'I Told You So'
When spoken with a rising intonation, it acts like a tag question ('...right?'). In assertive contexts, especially when shortened to だろ！, it carries an 'I told you so' nuance, used when the speaker's previous prediction is proven correct.

4. Wondering with だろうか
The pattern だろうか is used for self-questioning or 'wondering' aloud. It is less direct than a standard か question and often appears in internal monologues or formal writing.

5. Gender and Register
In daily conversation, だろう is primarily used by men and can sound blunt. Women often prefer でしょう to sound softer. However, in written Japanese (essays, news), だろう is the standard, gender-neutral form for speculation.

Examples (6)

  1. 明日は雨が降るだろう。

    It will probably rain tomorrow.

    Word by Word: Tomorrow (topic) rain fall probably.

    A standard prediction about the weather using a verb in the plain form followed by だろう. This is common in weather reports.

  2. 試験は難しいだろう。

    The exam will probably be difficult.

    Word by Word: Exam (topic) difficult probably.

    Making a conjecture about a future event using an い-adjective.

  3. 彼はもう行っただろう。

    He probably already went.

    Word by Word: He (topic) already went probably.

    Using the た form (past tense) to guess about a completed action.

  4. ほら、言っただろ！

    See, I told you so!

    Word by Word: Look, said (past) probably!

    Demonstrates the shortened casual form だろ used to emphasize that the speaker was right (an 'I told you so' nuance).

  5. どうしてこんなことになったのだろうか。

    I wonder why it turned out like this.

    Word by Word: Why this kind of thing became (explanatory) probably (question)?

    The pattern だろうか is used for self-questioning or expressing a sense of wonder/doubt.

  6. 昨日は寒かっただろう。

    It must have been cold yesterday, right?

    Word by Word: Yesterday (topic) was cold probably.

    Combining the past tense of an い-adjective with だろう to guess about a past state.

Common Mistakes

  • Adding だ before だろう with nouns or な-adjectives.

    彼は学生だだろう。
    彼は学生だろう。

    Unlike the polite form でしょう, which replaces です, だろう replaces だ. You should never have だ and だろう next to each other.

  • Using だろう with adverbs that imply very low certainty like もしかしたら (perhaps).

    もしかしたら雨だろう。
    たぶん雨だろう。

    だろう expresses a relatively strong conviction. Using it with もしかしたら (perhaps), which implies low certainty, is unnatural. Use たぶん (probably) instead.

How It Connects

Tap a pattern to see what it builds on and what it leads to.

だろうLevel 2Probably

Learn This First

だろう is the casual presumptive form of the copula. To understand it, learners must first be familiar with the basic casual copula 'だ' and the concept of politeness levels, as 'だろう' is the informal version of 'でしょう'. It is also helpful to distinguish its use as a guess from its use as a confirmation marker.

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