Understanding でしょう and だろう in Japanese Grammar

Probability, Assumption, or Seeking Agreement in Japanese

The Ultimate Guide to でしょう and だろう: Mastering Japanese Guessing and Speculation

Do you ever wonder how to say “it’s probably raining” or “he’s probably tired” in Japanese? 🤔 Knowing how to express uncertainty and speculation is a key skill. This is where the Japanese grammar points でしょう (deshou) and だろう (darou) come in! They are essential for a variety of conversational situations. In this comprehensive guide, we’ll break down everything you need to know, from the basic rules to advanced usage and common mistakes. By the end, you’ll be able to use these expressions with confidence. So let’s dive in and master the art of guessing in Japanese!

What Is でしょう and だろう? Explanation & Overview

At their core, deshou and darou are used to express speculation or probability. They are the Japanese equivalents of phrases like “probably,” “likely,” or “I think that…” The difference between them is primarily one of formality.

Darou (だろう) is the plain form, and it’s informal. Think of it as something you’d use with friends or family.

Deshou (でしょう) is the polite form. This is the version you’d use in more formal situations, like with your boss, a teacher, or a stranger.

Both deshou and darou can be attached to various parts of speech. They often follow verbs, adjectives, and nouns. The general pattern is:

Verb/Adjective/Noun + deshou/darou

Here’s a simple summary:

• Plain Form: Verb/i-adjective (plain form) + darou
• Plain Form: Noun/na-adjective stem + darou
• Polite Form: Verb/i-adjective (plain form) + deshou
• Polite Form: Noun/na-adjective stem + deshou

For a quick reference, remember this: darou is for casual talk, deshou is for polite talk.

3) Everyday Sentences Using でしょう and だろう: 10 Common Examples

Here are some natural, everyday sentences to get you started.

1. 明日、雨が降るだろう。 (Ashita, ame ga furu darou.) – It will probably rain tomorrow.
2. 彼はもう家に帰ったでしょう。 (Kare wa mou ie ni kaetta deshou.) – He’s probably already gone home.
3. このケーキは甘いでしょうね。 (Kono keeki wa amai deshou ne.) – This cake is probably sweet, isn’t it?
4. 田中さんは学生だろう。 (Tanaka-san wa gakusei darou.) – Mr. Tanaka is probably a student.
5. 疲れただろう？ (Tsukareta darou?) – You must be tired, right?
6. 彼女は来るでしょうか。 (Kanojo wa kuru deshou ka.) – Do you think she will come?
7. あの人は日本人だろう。 (Ano hito wa Nihonjin darou.) – That person is probably Japanese.
8. 寒かっただろう。 (Samukatta darou.) – It must have been cold.
9. 今日は忙しいだろう。 (Kyou wa isogashii darou.) – I guess you’re busy today.
10. これは便利でしょう。 (Kore wa benri deshou.) – This is probably convenient.

4) When to Use でしょう and だろう: All Key Situations

Both deshou and darou are used in a number of specific situations. Understanding these contexts is crucial for using them correctly.

• To express speculation or probability: This is their most common use. You use them when you are not 100% sure about something but have a good feeling or some evidence.
  • Example: 彼はまだ寝ているでしょう。 (Kare wa mada neteiru deshou.) – He’s probably still sleeping.
  • Caution: Don’t use this when you are certain. If you know for a fact he is sleeping, you’d just say 「彼はまだ寝ています。」 (Kare wa mada neteimasu.)
• To make a polite suggestion or soft invitation: This use is especially common with deshou. It’s a gentle way of inviting someone to do something.
  • Example: 映画に行きませんか？ 楽しいでしょう。 (Eiga ni ikimasen ka? Tanoshii deshou.) – Why don’t we go to the movies? It’ll probably be fun, right?
  • Caution: Using this for a direct command can sound a bit condescending. It’s best used as a gentle suggestion.
• To confirm a fact or seek agreement (when used as a question): When you add a rising intonation at the end of deshou, it turns into a question. You’re asking for the other person’s agreement.
  • Example: この問題は難しいでしょう？ (Kono mondai wa muzukashii deshou?) – This problem is difficult, isn’t it?
  • Caution: The darou form is less common for this purpose, though you might hear it among very close friends.
• To state a conclusion based on a premise: You use darou to state what you believe to be the case based on what you already know.
  • Example: あんなに勉強したから、試験は簡単だろう。 (Anna ni benkyou shita kara, shiken wa kantan darou.) – Since you studied so hard, the test will probably be easy.
  • Caution: This is a statement of your own conclusion, not an absolute fact.

5) Conjugation Rules

Using deshou and darou is simpler than many other Japanese grammar points because the particles themselves don’t change. You just need to know how to connect them to different word types.

Here’s the logic:

• Verbs: Attach deshou or darou to the plain form of the verb (dictionary form, ta-form, etc.).
• i-adjectives: Attach deshou or darou to the plain form of the i-adjective.
• na-adjectives: Attach deshou or darou to the stem of the na-adjective (without the final na).
• Nouns: Attach deshou or darou directly to the noun.

Let’s look at some examples:

• Verbs:
  • 行く (iku, to go): 行くだろう (iku darou) / 行くでしょう (iku deshou) – will probably go
  • 行った (itta, went): 行っただろう (itta darou) / 行ったでしょう (itta deshou) – probably went
• i-adjectives:
  • 美味しい (oishii, delicious): 美味しいだろう (oishii darou) / 美味しいでしょう (oishii deshou) – is probably delicious
• na-adjectives:
  • 静か (shizuka, quiet): 静かだろう (shizuka darou) / 静かでしょう (shizuka deshou) – is probably quiet
• Nouns:
  • 学生 (gakusei, student): 学生だろう (gakusei darou) / 学生でしょう (gakusei deshou) – is probably a student

A quick checklist for usage:

• ✅ Verb Form: Use the plain form.
• ✅ Adjective Form: Use the plain form for i-adjectives; remove the na for na-adjectives.
• ✅ Noun Form: Attach directly.
• ✅ Placement: At the end of the sentence or clause.
• ✅ Polite vs. Plain: Deshou for polite, darou for plain.

6) でしょう and だろう Grammar Rules You Need to Know

Here are a few specific grammar rules and nuances to help you use these expressions like a native speaker.

1. Rule: Using darou to confirm a fact is rare in conversation.
   • Stating “Kare wa Gakusei darou?” sounds a bit like you’re talking to yourself or are very close with the person. For confirmation, deshou? is more standard.
   • Example: 彼女は先生でしょう？ (Kanojo wa sensei deshou?) – She’s a teacher, isn’t she?
   • Note: While you can use darou for questions, deshou is much more common and safer to use.
2. Rule: Deshou as a question often implies you have a strong belief in the answer.
   • When you ask with deshou, it’s not a neutral question. It’s more of a leading question, expecting a “yes” or “I agree” response.
   • Example: この映画、面白かったでしょう？ (Kono eiga, omoshirokatta deshou?) – This movie was interesting, wasn’t it?
   • Note: This is a great way to confirm shared feelings or opinions.
3. Rule: Darou can sound a bit rough or blunt, especially if used with a confident tone.
   • While darou is the plain form, using it too assertively can sound like you are stating a fact rather than a guess.
   • Example: 彼が犯人だろう。 (Kare ga hannin darou.) – He’s the culprit. (This sounds more like an accusation than a guess.)
   • Note: To soften it, you can add a particle like ne or yo (e.g., Kare ga hannin darou ne.).
4. Rule: The negative form follows the same pattern as plain form.
   • You attach deshou or darou to the plain negative form of the verb or adjective.
   • Example: 彼女は来ないだろう。 (Kanojo wa konai darou.) – She probably won’t come.
   • Example: 難しくないでしょう。 (Muzukashiku nai deshou.) – It probably isn’t difficult.

7) Important Tips for Using でしょう and だろう Correctly

• Tip 1: Remember the “Formality Filter”
  • The most common mistake is mixing up formal and informal situations. Ask yourself: “Am I talking to a friend or someone I need to show respect to?” Use deshou for the latter, darou for the former.
  • Example: To your friend: 今日は忙しいだろう。 To your boss: 今日は忙しいでしょう。
• Tip 2: Use ne and yo to soften the tone.
  • Adding particles like ne (seeking agreement) or yo (stating your opinion) can make your sentence sound much more natural and less blunt.
  • Example: この本、難しいでしょう？ (Kono hon, muzukashii deshou?) – This book is difficult, isn’t it? (Seeking agreement)
• Tip 3: Don’t confuse it with other guessing expressions.
  • There are other ways to express speculation, such as kamoshirenai (might, may). Deshou/darou implies a stronger probability.
  • Use deshou/darou when you feel it’s likely to be true. Use kamoshirenai when you think it might be true, but there’s a higher degree of uncertainty.
• Tip 4: Watch out for rising intonation.
  • A rising intonation turns deshou into a question. A flat or falling intonation makes it a statement.
  • Statement: それは高いでしょう。 (That’s probably expensive.)
  • Question: それは高いでしょう？ (That’s expensive, isn’t it?)

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

❌ Mistake 1: Using darou in a polite setting.

• Wrong: 先生はもう行っただろう。 (Sensei wa mou itta darou.) – The teacher probably already went.
• Right: 先生はもう行かれたでしょう。 (Sensei wa mou ikareta deshou.) – The teacher probably already went.
• Why: You should use the polite form deshou and respect language when talking about or to a teacher.

❌ Mistake 2: Attaching to the wrong verb form.

• Wrong: 行きますでしょう。 (Ikimasu deshou.) – (Incorrect combination of polite and plain forms.)
• Right: 行くでしょう。 (Iku deshou.) – I’ll probably go.
• Why: deshou and darou attach to the plain form of the verb, not the masu form.

❌ Mistake 3: Using them when you are certain.

• Wrong: 私は明日東京へ行くだろう。 (Watashi wa ashita Toukyou e iku darou.) – I will probably go to Tokyo tomorrow.
• Right: 私は明日東京へ行きます。 (Watashi wa ashita Toukyou e ikimasu.) – I will go to Tokyo tomorrow.
• Why: You don’t speculate about your own certain actions. deshou/darou are for external situations or when you are not the subject of the sentence.

❌ Mistake 4: Using them to ask for permission.

• Wrong: 窓を開けてもいいでしょうか。 (Mado o akete mo ii deshou ka.) – May I open the window?
• Right: 窓を開けてもいいですか。 (Mado o akete mo ii desu ka.) – May I open the window?
• Why: The standard way to ask for permission is with -te mo ii desu ka. deshou ka asks for a guess or a fact confirmation.

9) 20 でしょう and だろう Example Sentences for Better Understanding

Here are 20 more examples to solidify your understanding. Pay close attention to the context and the word that precedes deshou/darou.

1. この本は面白くないだろう。 (Kono hon wa omoshiroku nai darou.) – This book is probably not interesting.
2. 彼はもう仕事が終わったでしょう。 (Kare wa mou shigoto ga owatta deshou.) – His work is probably already finished.
3. 明日は晴れるだろうか。 (Ashita wa hareru darou ka.) – I wonder if it will be sunny tomorrow.
4. 彼女は元気でしょう。 (Kanojo wa genki deshou.) – She’s probably well.
5. あのレストランは美味しいだろう。 (Ano resutoran wa oishii darou.) – That restaurant is probably delicious.
6. こんな寒い日には、誰も外に出ないでしょう。 (Konna samui hi ni wa, dare mo soto ni denai deshou.) – On such a cold day, nobody will probably go outside.
7. 彼は英語を話すでしょう。 (Kare wa eigo o hanasu deshou.) – He probably speaks English.
8. その話は本当だろうか。 (Sono hanashi wa hontou darou ka.) – I wonder if that story is true.
9. 今日は忙しいでしょう。 (Kyou wa isogashii deshou.) – You’re probably busy today. (Polite)
10. これは山田さんの傘でしょう。 (Kore wa Yamada-san no kasa deshou.) – This is probably Mr. Yamada’s umbrella.
11. 彼女はまだ高校生だろう。 (Kanojo wa mada koukousei darou.) – She’s probably still a high school student.
12. この靴は少し小さいだろう。 (Kono kutsu wa sukoshi chiisai darou.) – These shoes are probably a little small.
13. 彼は遅れるだろう。 (Kare wa okureru darou.) – He’s probably going to be late.
14. この答えは正しいでしょうか。 (Kono kotae wa tadashii deshou ka.) – Is this answer probably correct?
15. 宿題は終わっただろう？ (Shukudai wa owatta darou?) – You finished your homework, didn’t you?
16. 彼らはもう着いたでしょう。 (Karera wa mou tsuita deshou.) – They’ve probably already arrived.
17. この機械は古いだろう。 (Kono kikai wa furui darou.) – This machine is probably old.
18. 今日は暑いだろう。 (Kyou wa atsui darou.) – It’s probably hot today.
19. 彼はこの仕事を一人でやるでしょう。 (Kare wa kono shigoto o hitori de yaru deshou.) – He’ll probably do this work by himself.
20. お母さんは怒っているだろう。 (Okaasan wa okotteiru darou.) – Mom is probably angry.

10) でしょう and だろう Fill-in-the-Blank Exercise: Test Your Knowledge (20 Qs)

Ready to test what you’ve learned? Complete these sentences with the correct form of deshou or darou.

1. 彼はもうすぐ来る___。 (kuru)
2. この映画は面白い___。 (omoshiroi)
3. 彼は医者___。 (isha)
4. 明日は晴れる___か。 (hareru)
5. その話は本当___。 (hontou)
6. あなたは疲れた___？ (tsukareta)
7. このラーメンは辛くない___。 (karaku nai)
8. 田中さんはもう寝た___。 (neta)
9. 日本語の勉強は大変___。 (taihen)
10. 彼女は学生___。 (gakusei)
11. それは高い___。 (takai)
12. 明日は雨が降る___。 (furu)
13. あの人は日本人___。 (nihonjin)
14. 彼はもう家に帰った___。 (kaetta)
15. 彼は仕事で忙しい___。 (isogashii)
16. その本は古くない___。 (furuku nai)
17. 彼はもうすぐ着く___。 (tsuku)
18. この問題は難しい___か。 (muzukashii)
19. 彼は明日来る___。 (kuru)
20. この電車はもう行った___。 (itta)

11) Check Your Answers — Complete Sentences

1. 彼はもうすぐ来るだろう。
2. この映画は面白いでしょう。
3. 彼は医者だろう。
4. 明日は晴れるでしょうか。
5. その話は本当だろう。
6. あなたは疲れただろう？
7. このラーメンは辛くないだろう。
8. 田中さんはもう寝たでしょう。
9. 日本語の勉強は大変でしょう。
10. 彼女は学生でしょう。
11. それは高いでしょう。
12. 明日は雨が降るだろう。
13. あの人は日本人だろう。
14. 彼はもう家に帰ったでしょう。
15. 彼は仕事で忙しいでしょう。
16. その本は古くないだろう。
17. 彼はもうすぐ着くでしょう。
18. この問題は難しいでしょうか。
19. 彼は明日来るでしょう。
20. この電車はもう行ったでしょう。

12) Frequently Asked Questions (20)

Q1: What’s the main difference between deshou and darou?

A: The main difference is formality. Deshou is polite and used in formal or polite situations. Darou is the plain form, used with close friends and family.

Q2: Can I use darou when talking to my boss?

A: No, it’s generally best to avoid darou with a boss or in any formal setting. Stick with deshou to show respect.

Q3: Can deshou and darou be used with masu form?

A: No. Deshou and darou always attach to the plain form of a verb or adjective. For instance, you should say kuru deshou, not kimasu deshou.

Q4: Is deshou always a question?

A: No, it’s a statement of speculation unless you use a rising intonation at the end. For example, Ame ga furu deshou. means “It will probably rain.” Ame ga furu deshou? means “It will probably rain, right?”

Q5: What’s the negative form?

A: You attach deshou or darou to the plain negative form. For example, ikanaidarou (probably won’t go) or oishikunaideshou (probably not delicious).

Q6: Can I use deshou ka to ask a question?

A: Yes. Deshou ka is a polite way to ask a question that seeks the listener’s opinion or confirmation of a fact. It’s often used when you’re not entirely sure of the answer.

Q7: How is deshou/darou different from kamoshirenai?

A: Deshou/darou indicates a higher degree of probability (maybe 70-80%). Kamoshirenai (maybe, might) suggests a lower probability (around 30-50%). For example, kuru darou means “will probably come,” while kuru kamoshirenai means “might come.”

Q8: Can darou be used with politeness?

A: No, darou is inherently informal and casual. Using it in a polite context can sound rude or abrupt.

Q9: Do I need da before darou with a noun?

A: No, you do not use da before darou. You attach darou directly to the noun. For example, gakusei darou, not gakusei da darou.

Q10: What’s the difference between deshou and desu ne?

A: Deshou is for speculation, while desu ne is for confirming something you already know or a shared observation. Samui deshou ne means “It’s probably cold, isn’t it?” while Samui desu ne means “It’s cold, isn’t it?”

Q11: Can deshou be used to ask for a suggestion?

A: Yes, in a gentle way. For instance, “どこへ行きますか？” (Doko e ikimasu ka?) is a direct question, but “どこへ行きたいでしょうか。” (Doko e ikitai deshou ka?) is a more indirect, softer way to ask where someone might want to go.

Q12: Is there a simpler way to remember the conjugation?

A: Yes, just remember that deshou and darou follow the same word types as desu and da. The form is very similar.

Q13: Can deshou be used to soften a request?

A: Yes, it can make a request sound less direct and more polite. For example, instead of shite kudasai, you might say shite kudasaru deshou ka.

Q14: How does it work with adjectives?

A: For i-adjectives, attach directly: Samui deshou. For na-adjectives, remove the na and attach: Shizuka deshou.

Q15: What if I don’t know the plain form of a verb?

A: It’s crucial to know the plain forms of verbs to use deshou/darou correctly. If you’re unsure, you can look it up or practice with a plain form verb chart.

Q16: Can darou be used to express a strong opinion?

A: Yes, depending on the tone. A confident, falling tone with darou can sound like you are stating a strong belief, rather than a mere guess.

Q17: Is it common to use deshou with wa?

A: Yes, phrases like “wa deshou” are common. For example, Sou desu wa deshou. (That’s probably so.)

Q18: Is there a common mistake with nouns?

A: Yes, learners sometimes add an extra da after a noun, like Gakusei da darou, which is incorrect. The correct form is Gakusei darou.

Q19: Can deshou be used for questions about past events?

A: Yes. You just attach it to the plain past tense form. For example, Kare wa kita deshou ka. (Do you think he came?).

Q20: What are some other polite forms similar to deshou?

A: You can use to omoimasu (I think that) as a very polite alternative for speculation. For example, Ame ga furu to omoimasu.

13) Key Takeaways: Summary & Important Points

• でしょう (deshou) and だろう (darou) express speculation or probability.
• Deshou is polite, used in formal settings. Darou is plain, used with friends and family.
• They attach to the plain form of verbs, i-adjectives, and nouns. For na-adjectives, they attach to the stem.
• When used as a question with rising intonation, they ask for confirmation or agreement.
• Don’t use them for things you are certain about.
• Avoid mixing deshou with masu form verbs. Always use the plain form.
• Remember the difference in probability: deshou/darou (high probability) vs. kamoshirenai (lower probability).

14) Conclusion

Mastering deshou and darou is a huge step in sounding more natural and confident in Japanese. These simple but powerful phrases allow you to express a whole new range of feelings and ideas, from gentle suggestions to educated guesses. Remember the key difference between the polite and plain forms, and you’ll be well on your way.

The next step is to put this knowledge into practice! Try to use deshou and darou in your next conversation.