Japanese Grammar: だろう (darou) – Expressing Probability and Conjecture

Japanese Grammar: だろう (darou) – Expressing Probability and Conjecture
Meaning & Usage

✨ Basic Meaning

‘Probably’, ‘I think’, or ‘Right?’ (Conjecture/Confirmation)

🎯 Primary Function

To express the speaker’s conjecture, guess, or to seek the listener’s agreement in a plain/casual style.

📋 Grammar Structure

Verb (Plain/Dictionary Form) + だろう
I-Adjective + だろう
Na-Adjective (no [da]) + だろう
Negative Form (Verb-nai / Adj-nai / Noun + de wa nai) + だろう

🎭 Usage Contexts

🏢 Formal Situations

Generally avoided in formal speech; ‘deshou’ is used instead. However, it appears in formal written reports.

😊 Informal Situations

Very common in casual conversations among friends or when a superior speaks to a subordinate.

✍️ Written Language

Used in essays, novels, and news reports to express a logical guess or objective probability.

🗣️ Spoken Language

Frequent in casual speech, often used to ask ‘don’t you agree?’ with rising intonation.

💡 Common Applications

Expressing Uncertainty
Used when the speaker is making a guess about a future event or unknown fact with some level of certainty.
Example: 明日は晴れるだろう。
Seeking Confirmation (Tag Question)
When used with a rising intonation, it functions like ‘…right?’ or ‘…don’t you agree?’ to confirm information with the listener.
Example: 君も行くだろう?
Casual Written Style
Often used in academic papers or newspaper editorials (sometimes as ‘dearou’) to state a logical conclusion or prediction.
Example: この傾向は続くであろう。
📊
Frequency
High
🎚️
Difficulty
N5/N4 (Introduced early, but nuances are N4)
Example Sentences
Example #1
明日、雨が降るだろう。
Furigana: あした、あめがふるだろう。
Romaji: Ashita, ame ga furu darou.
English: It will probably rain tomorrow.
Example #2
彼はもう来ないだろう。
Furigana: かれはもうこないだろう。
Romaji: Kare wa mou konai darou.
English: He probably won’t come anymore.
Example #3
このテストは難しいだろう。
Furigana: このテストはむずかしいだろう。
Romaji: Kono tesuto wa muzukashii darou.
English: This test will probably be difficult.
Example #4
あのレストランの料理はおいしいだろう。
Furigana: あのレストランのりょうりはおいしいだろう。
Romaji: Ano resutoran no ryouri wa oishii darou.
English: The food at that restaurant is probably delicious.
Example #5
君もパーティーに来るだろう?
Furigana: きみもパーティーにくるだろう?
Romaji: Kimi mo paatii ni kuru darou?
English: You are coming to the party too, right?
Example #6
彼女は大学生だろう。
Furigana: かのじょはだいがくせいだろう。
Romaji: Kanojo wa daigakusei darou.
English: She is probably a college student.
Example #7
昨日は、彼はお忙しかっただろう。
Furigana: きのうは、かれはいそがしかっただろう。
Romaji: Kinou wa, kare wa isogashikatta darou.
English: He was probably busy yesterday.
Example #8
あの人は静かだろう。
Furigana: あのひとはしずかだろう。
Romaji: Ano hito wa shizuka darou.
English: That person is probably quiet (gentle).
Example #9
彼にとって、簡単ではなかっただろう。
Furigana: かれにとって、かんたんではなかっただろう。
Romaji: Kare ni totte, kantan de wa nakatta darou.
English: I think it wasn’t easy for him.
Example #10
もう遅いから、彼女は寝ているだろう。
Furigana: もうおそいから、かのじょはねているだろう。
Romaji: Mou osoi kara, kanojo wa nete iru darou.
English: It’s already late, so she’s probably sleeping.
Notes & Nuances

📌 Important Points

Conjecture vs. Assertion
It softens a statement from a factual claim to a guess.
Example: 明日は雨だろう。 (Probably rain) vs 明日は雨だ。 (It is rain)
Intonation Matters
With a rising tone, it specifically invites the listener to agree, similar to the particle ‘ne’.
Example: だろう? (Rising intonation)

⚠️ Common Mistakes

❌ 元気だだろう (Genki da darou)
✅ 元気だろう (Genki darou)
You must not use ‘da’ with ‘darou’. For Na-Adjectives and Nouns, just add ‘darou’ directly to the stem.
❌ Confusing rising/falling intonation.
✅ だろう? (Darou? / rising) vs だろう。(Darou. / falling)
Using falling intonation for a question can sound like you are forcing your opinion rather than asking for confirmation.

🏛️ Cultural Context

Politeness Level: Informal. Using ‘darou’ to a social superior can sound rude or overly assertive.
Social Situations: Commonly used by males in casual speech, though anyone can use it in written form.
Regional Variations: In some regions, ‘yaro’ is used instead of ‘darou’ (Kansai dialect).

🔍 Subtle Differences

だろう vs でしょう
‘Darou’ is plain/casual; ‘Deshou’ is polite/formal.
When to use: Use ‘Darou’ with friends; ‘Deshou’ with teachers or strangers.
だろう vs と思う
‘To omou’ is a personal thought; ‘Darou’ sounds like a slightly more objective prediction or a call for agreement.
When to use: Use ‘Darou’ for general probability or confirmation.

📝 Conjugation Notes

‘Darou’ is the plain/informal form of ‘Deshou’. It follows the same grammatical rules: direct attachment to nouns, na-adjective stems, i-adjectives, and plain-form verbs.

🔊 Pronunciation Tips

When used as a question, ensure the pitch rises clearly on the last syllable. In casual speech, it is sometimes shortened to ‘rou’ in certain dialects, but stick to ‘darou’ for clarity.

🧠 Memory Tips

Think of ‘Darou’ as the ‘Rough/Plain’ cousin of ‘Deshou’. If you want to say ‘Probably’ in a casual way, use ‘Darou’.

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