Understanding でしょう and だろう in Japanese Grammar

Probability, Assumption, or Seeking Agreement in Japanese

Have you ever wondered what 〜でしょう and 〜だろう mean in Japanese? Or maybe you’ve asked yourself, “When should I use でしょう instead of だろう?” If you’ve studied Japanese for a while, these two little words can feel confusing—but they are absolutely essential to mastering natural conversation.

The good news? Both 〜でしょう and 〜だろう are easier than they first appear. They are used every day in Japanese to express probability, assumption, or seeking agreement. Think of them as ways to say “probably,” “right?” or “I guess” in English. Once you understand how to use them, you’ll sound more natural and confident when speaking Japanese.

👉 Quick answer for beginners:

• でしょう is the polite form, often used in daily conversations, news reports, or formal settings.
• だろう is the casual form, mostly used by men or in informal speech among friends.

For example:

• 明日は雨が降るでしょう。
  → It will probably rain tomorrow. (polite)
• 彼は来ないだろう。
  → He probably won’t come. (casual)

These forms appear everywhere—from textbooks and JLPT exams to anime and real conversations in Japan. According to The Japan Times’ A Dictionary of Basic Japanese Grammar, learners often encounter them in early intermediate stages because they carry nuance that goes beyond simple translation.

In this guide, we’ll break down everything you need to know about 〜でしょう and 〜だろう step by step:

• Their meaning and background
• Common everyday examples
• Practical usage situations
• Conjugation rules and grammar breakdown
• Important tips and common mistakes
• Exercises and answers to test your knowledge
• FAQs and summary takeaways

By the end of this article, you’ll not only understand these forms but also feel ready to use them naturally in your own conversations.

What Is 〜でしょう/だろう? Explanation and Overview

At its core, 〜でしょう and 〜だろう are sentence-ending expressions in Japanese. They are used when the speaker wants to show probability, assumption, or ask for confirmation. In English, these can often translate as:

• “probably”
• “I guess”
• “it seems”
• “right?”
• “won’t it?”

While they share the same basic function, the difference lies mainly in formality and tone.

〜でしょう (deshou)

• Polite form of expressing probability or assumption.
• Often used in formal settings like the news, public speeches, workplace communication, or polite conversations.
• Can also be used as a softener, making a statement sound less direct.

👉 Example:

• 明日は雪が降るでしょう。
  → It will probably snow tomorrow.

Here, the speaker is making a prediction but keeping it polite and neutral.

〜だろう (darou)

• Casual form, used more in spoken language, often among friends or in informal contexts.
• Commonly used by men, but women also use it depending on the situation.
• Feels more assertive than でしょう, though still expresses probability.

👉 Example:

• 彼はもう家に帰っただろう。
  → He has probably gone home already.

Politeness Difference

Think of でしょう as the softer, more polite choice, and だろう as the casual, sometimes more confident choice.

Asking for Confirmation

Both can also be used to seek agreement, similar to adding “right?” or “isn’t it?” in English.

• これは簡単でしょう？
  → This is easy, isn’t it?
• あの映画は面白かっただろう？
  → That movie was interesting, right?

This makes them not only about probability, but also about shared understanding between speaker and listener.

Everyday Sentences Using 〜でしょう/だろう: 10 Common Examples

The best way to understand 〜でしょう and 〜だろう is by seeing them in action. Below are 10 everyday Japanese sentences with their English translations. Each example shows how these forms are used in real conversations.

With 〜でしょう (polite)

1. 明日は雨が降るでしょう。
   → It will probably rain tomorrow.
2. 先生もこの意見に賛成するでしょう。
   → The teacher will probably agree with this opinion.
3. 彼女はもう来るでしょう。
   → She will probably come soon.
4. この料理は美味しいでしょう？
   → This dish is delicious, isn’t it?
5. 会議は長くなるでしょうね。
   → The meeting will probably be long, right?

With 〜だろう (casual)

6. 彼は今日、学校に来ないだろう。
   → He probably won’t come to school today.
7. もう夜だから、店は閉まっているだろう。
   → Since it’s already night, the store is probably closed.
8. 明日の試験は難しいだろう。
   → Tomorrow’s test will probably be difficult.
9. これは彼が書いた本だろう？
   → This is the book he wrote, right?
10. そんなことは誰でも知っているだろう。
    → Everyone probably knows that.

Key Point to Notice

• でしょう sounds polite, neutral, and is safe to use in most contexts.
• だろう feels casual and can sometimes sound stronger or more assertive.

By practicing these sentences aloud, you’ll start to feel the nuance and rhythm of both forms.

When to Use 〜でしょう/だろう: All the Key Situations

Understanding when to use 〜でしょう and 〜だろう is just as important as knowing what they mean. These forms are not random—they appear in specific contexts where the speaker wants to show probability, assumption, or seek agreement. Below are the key situations where you’ll naturally use them.

1. Making Predictions About the Future

Use でしょう or だろう when you’re guessing or predicting something that hasn’t happened yet.

• 明日は晴れるでしょう。
  → It will probably be sunny tomorrow.
• 彼は遅れて来るだろう。
  → He’ll probably come late.

2. Expressing Probability or Assumption

When you’re not 100% sure but reasonably confident about something, these forms help soften your statement.

• その映画は面白いでしょう。
  → That movie is probably interesting.
• 彼女は今、図書館にいるだろう。
  → She’s probably at the library now.

3. Asking for Agreement or Confirmation

Both can be used like English “right?” or “isn’t it?” to involve the listener.

• この問題は簡単でしょう？
  → This problem is easy, isn’t it?
• あの人は親切だっただろう？
  → That person was kind, right?

4. Softening Statements

でしょう is often used to avoid sounding too direct, especially in formal situations. It makes your statement feel more polite and less imposing.

• あなたも来るでしょう。
  → You’ll come too, won’t you? (gentle and polite)

5. Showing Confidence or Conviction

だろう can sound more assertive, sometimes closer to “I bet” or “I’m sure.”

• 彼はきっと勝つだろう。
  → He will surely win, I bet.

6. In the News or Public Announcements

News reports often use でしょう to keep predictions polite and neutral.

• 台風は明日の夜、九州に上陸するでしょう。
  → The typhoon will probably hit Kyushu tomorrow night.

7. In Inner Thoughts or Narration

Writers and speakers often use だろう to express internal assumptions or narrative guesses.

• 彼はもう寝ているだろう。
  → He’s probably already asleep.

8. In Questions with Rising Intonation

When used with a rising tone, both forms can make your statement sound like a question.

• 行くでしょう？
  → You’re going, right?
• 彼も来るだろう？
  → He’s coming too, isn’t he?

✅ Key takeaway:

• Use でしょう in polite, neutral, or formal settings.
• Use だろう in casual, confident, or inner-thought situations.

Conjugation Rules for 〜でしょう and 〜だろう

Both でしょう and だろう come from the copula だ (the plain form of “to be”). They attach to the end of sentences, so you don’t need complicated conjugation patterns like with verbs. Still, there are a few important things to know about how they behave with different forms.

Basic Forms

👉 Example:

• 明日は雨です → 明日は雨が降るでしょう。
• 明日は雨だ → 明日は雨が降るだろう。

Polite vs. Casual Conjugation

• Polite: Use でしょう after verbs, adjectives, or nouns in polite contexts.
• Casual: Use だろう after plain forms (dictionary form of verbs, adjectives, or nouns + だ).

Verb Conjugation Examples

Adjective Conjugation Examples

Noun Conjugation Examples

Negative + でしょう/だろう

You can also combine them with negative forms to guess about something not being true.

• 彼は来ないでしょう。
  → He probably won’t come.
• あれは本当ではないだろう。
  → That’s probably not true.

Past Tense + でしょう/だろう

To express probability about the past, attach them to the past tense.

• 彼は昨日、忙しかったでしょう。
  → He was probably busy yesterday.
• もう家に帰っただろう。
  → He has probably gone home already.

✅ Key tip: Unlike verbs, でしょう and だろう themselves don’t conjugate much. What changes is the word before them (verb, adjective, or noun).

Grammar Rules You Need to Know for 〜でしょう and 〜だろう

While 〜でしょう and 〜だろう look simple, they follow some important grammar rules. Understanding these rules will help you avoid common mistakes and make your Japanese sound more natural.

1. Position in the Sentence

• Both でしょう and だろう always appear at the end of a sentence.
• They cannot stand alone without a clause before them.

👉 Example:

• 正しい答えはこれでしょう。
  → This is probably the correct answer.
• 彼は来ないだろう。
  → He probably won’t come.

2. Politeness Levels

• でしょう = polite, safe for formal and neutral conversations.
• だろう = casual, often used among friends, in writing, or inner thoughts.

👉 Be careful not to use だろう in a workplace or with strangers—it can sound too blunt.

3. Rising Intonation = Question

When spoken with a rising intonation, でしょう and だろう turn into confirmation questions, similar to English “isn’t it?” or “right?”.

• これは簡単でしょう？
  → This is easy, isn’t it?
• 彼も来るだろう？
  → He’s coming too, right?

4. Past Tense Use

When referring to the past, attach them after past tense verbs, adjectives, or nouns.

• 昨日は寒かったでしょう。
  → It was probably cold yesterday.
• 彼はもう帰っただろう。
  → He probably already went home.

5. With Negative Forms

You can attach them to negatives to express assumption or probability about something not being true.

• そんなことは起こらないでしょう。
  → That probably won’t happen.
• 彼はそんなことを言わなかっただろう。
  → He probably didn’t say that.

6. With “でしょうね” and “だろうね”

Adding ね makes the tone softer and invites agreement.

• 明日も暑いでしょうね。
  → It will probably be hot tomorrow, right?
• 彼も疲れているだろうね。
  → He’s probably tired too, huh?

7. With “でしょうか” (Polite Question)

When combined with か, でしょう becomes a polite way to ask about assumptions or possibilities.

• 明日、雨が降るでしょうか。
  → Will it rain tomorrow, I wonder?

👉 This form often appears in polite questions, interviews, or formal writing.

8. With Emphasis Words like “きっと” (Surely)

You can add adverbs to strengthen the meaning of probability.

• 彼はきっと合格するでしょう。
  → He will surely pass, I think.
• もう疲れているだろう。
  → He must be tired already.

9. Gender and Tone Nuance

• だろう is stereotypically more masculine, especially in anime or casual speech.
• Women also use it, but in daily polite conversations, they tend to prefer でしょう.

10. No Conjugation by Themselves

Remember, でしょう and だろう don’t change forms themselves. Instead, the verb, adjective, or noun before them takes the correct tense and form.

✅ In short:

• Use でしょう for polite and neutral predictions.
• Use だろう for casual, confident, or inner assumptions.
• Add intonation or particles to adjust meaning.

Important Tips for Using 〜でしょう and 〜だろう Correctly

Even though でしょう and だろう are simple in form, learners often stumble when trying to use them naturally. Here are some expert tips to help you avoid mistakes and sound more fluent in Japanese.

1. Choose Politeness Based on Situation

• Use でしょう in professional, formal, or neutral situations.
• Use だろう only with friends, family, or when expressing inner thoughts.

👉 Example:

• Formal: 先生も賛成するでしょう。
  → The teacher will probably agree.
• Casual: 彼は来ないだろう。
  → He probably won’t come.

2. Intonation Matters

• Falling intonation = prediction or assumption.
• Rising intonation = asking for agreement (“right?”).

👉 Example:

• 明日、雨が降るでしょう。 (falling tone → prediction)
• 明日、雨が降るでしょう？ (rising tone → confirmation)

3. Don’t Overuse in Writing

In formal writing (like reports or essays), でしょう is fine, but overusing it can make your sentences sound repetitive. Vary with other expressions like かもしれない (might/maybe) for softer guesses.

4. Watch Out for Gender Nuance

• In anime or drama, だろう is often used by male characters to sound confident or strong.
• In real life, both men and women use it casually, but women often prefer でしょう in mixed company for politeness.

5. Don’t Confuse with でしょうか

• でしょう = assumption/prediction.
• でしょうか = polite question.

👉 Example:

• 会議は長くなるでしょう。 (The meeting will probably be long.)
• 会議は長くなるでしょうか。 (Will the meeting be long, I wonder?)

6. Use with Softening Particles

Adding ね or よ changes the nuance:

• でしょうね = soft agreement or empathy.
• だろうよ = strong, assertive conviction (often in male speech).

👉 Example:

• 明日も暑いでしょうね。
  → It’ll be hot tomorrow too, won’t it?
• 彼は勝つだろうよ。
  → He’ll win for sure, I tell you.

7. Think of English Equivalents

• でしょう ≈ probably / it seems / isn’t it?
• だろう ≈ I guess / I bet / right?

Keeping this mental mapping will help you choose the correct one when speaking.

8. Practice Listening to Native Speakers

In real conversations, tone makes a huge difference. Watch Japanese news, dramas, or listen to podcasts to notice how でしょう and だろう are used. The NHK Easy News site is a great place to hear でしょう in natural, polite contexts.

✅ Quick Recap:

• Match politeness to context.
• Control your intonation.
• Use with care in writing.
• Add particles for nuance.
• Listen to real-life examples for better mastery.

Common Mistakes with 〜でしょう and 〜だろう and How to Fix Them

Even intermediate learners often slip up when using でしょう and だろう. These mistakes usually come from mixing politeness levels, intonation issues, or confusing them with other grammar patterns. Let’s look at the most common errors and how to correct them.

1. Using だろう in Formal Situations

❌ Mistake:

• 上司も理解するだろう。 (Said to your boss in a meeting)

This sounds too casual and can be seen as rude.

✅ Fix:

• 上司も理解するでしょう。
  → The boss will probably understand.

2. Forgetting the Rising Intonation in Confirmation Questions

❌ Mistake:

• これは簡単でしょう。 (said flatly)

This sounds like a statement, not a question.

✅ Fix:

• これは簡単でしょう？ (rising tone)
  → This is easy, isn’t it?

3. Mixing Up でしょう and でしょうか

❌ Mistake:

• 会議は長くなるでしょう？ (intended to politely ask)

This actually asks for confirmation, not politely wondering.

✅ Fix:

• 会議は長くなるでしょうか。
  → Will the meeting be long, I wonder?

4. Using Them Without Context

Learners sometimes tack on でしょう or だろう without a clear reason. This makes sentences sound unnatural.

❌ Mistake:

• 犬はかわいいでしょう。 (stated randomly)

✅ Fix: Use it only when expressing assumption or seeking agreement.

• 犬はかわいいでしょう？
  → Dogs are cute, aren’t they?

5. Confusing with かもしれない (might/maybe)

でしょう and だろう show a stronger degree of probability than かもしれない. Learners often use them interchangeably.

❌ Mistake:

• 彼は来るかもしれない。 (intended: He will probably come)

✅ Fix:

• 彼は来るでしょう / だろう。
  → He will probably come.

6. Overusing だろう in Writing

In essays or reports, using だろう can make your writing sound overly casual or biased.

✅ Fix: Prefer でしょう for polite written Japanese.

7. Using Past Without Proper Conjugation

❌ Mistake:

• 彼は昨日忙しいだろう。 (intended past tense)

✅ Fix:

• 彼は昨日忙しかっただろう。
  → He was probably busy yesterday.

8. Forgetting Gender/Tone Nuance

• Some learners use だろう too frequently after hearing it in anime (often by strong male characters). This can sound unnatural in real life, especially for female speakers in formal contexts.

✅ Fix: Balance your usage—reserve だろう for casual, friendly settings.

✅ Quick Rule:

• Use でしょう when in doubt—it’s safer and more polite.
• Use だろう only when the situation is casual and you want to sound confident or natural.

20 Example Sentences for Better Understanding

Below are 20 carefully chosen example sentences showing both でしょう (polite) and だろう (casual). They cover predictions, assumptions, confirmations, past tense, and negatives so you can see the full range of usage.

Predictions and Future Assumptions

1. 明日は雨が降るでしょう。
   → It will probably rain tomorrow.
2. 彼は来年大学に合格するでしょう。
   → He will probably pass the university entrance exam next year.
3. もうすぐ電車が来るだろう。
   → The train will probably come soon.
4. パーティーは楽しいだろう。
   → The party will probably be fun.

Expressing Probability in the Present

5. 彼女は今、図書館にいるでしょう。
   → She is probably at the library now.
6. 外は寒いでしょう。
   → It’s probably cold outside.
7. 彼はもう家に着いただろう。
   → He has probably already arrived home.
8. あの人は忙しいだろう。
   → That person is probably busy.

Confirmation / Agreement Seeking

9. この問題は簡単でしょう？
   → This problem is easy, isn’t it?
10. その映画は面白かったでしょう？
    → That movie was interesting, right?
11. 彼も来るだろう？
    → He’s coming too, right?
12. 君は知っているだろう？
    → You know, don’t you?

Past Probability

13. 昨日は寒かったでしょう。
    → It was probably cold yesterday.
14. 彼は昨日忙しかったでしょう。
    → He was probably busy yesterday.
15. その時、彼女は学校にいただろう。
    → She was probably at school at that time.
16. 試合はすでに終わっただろう。
    → The match has probably already finished.

Negative Probability

17. 彼は来ないでしょう。
    → He probably won’t come.
18. そんなことは起こらないでしょう。
    → That probably won’t happen.
19. 彼はそれを知らないだろう。
    → He probably doesn’t know that.
20. あの話は本当ではないだろう。
    → That story is probably not true.

vikas kumar

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Vikas Kumar is a dedicated language educator, content creator, and digital entrepreneur, best known as the co-founder of My Language Classes and The Curious Mind. With a strong focus on helping learners achieve fluency in English, Spanish, and Japanese, he has guided audiences worldwide through a diverse range of resources, including in-depth blog articles, engaging YouTube tutorials, and comprehensive Books.

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