“〜deshou・〜deshou ka”: Conjecture and Polite Questions [JLPT N4]

Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026

「明日は雨でしょう」「来るでしょう？」 — a guess, a “right?”, or a polite question.

The forecast says 「明日は雨でしょう」 — that's not “is,” it's “probably”

A weather forecast often ends with 「明日は雨でしょう」. That 「でしょう」 isn't 「です」 (“is”) — it's the conjecture “probably.” It's the tentative form of 「です」, and at N5 it does three jobs: conjecture (probably ~), confirmation (~right?), and polite question (~, I wonder?). Grab the “not fully certain, leaving room” feel and all three fall into place.

Three uses

• Conjecture “probably ~” (a judgment about the unsettled, often with たぶん・おそらく): 明日は雨でしょう.
• Confirmation “~right?” (you assume the listener knows too; rising tone): 田中さんも来るでしょう？
• Polite question “~, I wonder?” (でしょうか, softer than ですか): ご都合はいかがでしょうか？

Common thread: each is gentler than 「です・ですか」 — it doesn't state things flat-out.

How to Connect

Example sentences

• たぶん明日は晴れでしょう。(It'll probably be sunny tomorrow.) — conjecture
• 彼はおそらく合格するでしょう。(He'll probably pass.) — conjecture (with おそらく)
• 明日の会議、田中さんも来るでしょう？(Tanaka's coming to the meeting too, right?) — confirmation
• ご都合はいかがでしょうか？(Would that suit you?) — polite question (business)
• いつ来るでしょうか？(When might they come?) — polite question

⚠️ Where learners slip up

① 「でしょう」 isn't “is.” It's easy to use it like 「です」. 「明日は雨でしょう」 means “it'll probably rain,” not “tomorrow is rain.” It carries conjecture and leaves room.

② Attach the plain form. Before verbs and adjectives, use the plain form, not ます: 降るでしょう (✗ 降りますでしょう), 寒いでしょう.

③ でしょう ↔ だろう differ in politeness. Same meaning, but でしょう is polite and だろう is casual (common in men's speech). Don't use だろう with seniors or clients.

🔄 Nuance & comparison: でしょう / だろう / かもしれない

💡 How to remember this

The best thing 「でしょう」 does is help you sound less blunt. Unsure about tomorrow's weather? Say 「雨でしょう」. Want to ask politely? Use 「〜でしょうか」 — much softer than 「ですか」, and a real plus in business. Just remember its base color is “probably / maybe / leaving room,” and you won't mistake it for the flat 「です」.

❓ Quick FAQ

Q: でしょう vs かもしれない?

Different confidence: 「でしょう」 is a fairly sure guess (likely; 明日は雨でしょう); 「かもしれない」 is lower odds (maybe; 雨かもしれない).

Q: Why is 「いかがでしょうか」 better than 「いかがですか」?

「でしょうか」 adds a layer of softness and politeness — more appropriate when asking a superior or client. Among friends, 「ですか」 is fine.

🖊️ Practice Questions (5)

Q1. 「たぶん明日は___でしょう。」 (It will probably be sunny tomorrow) Which fits the blank?

(A) 晴れる　(B) 晴れ　(C) 晴れます　(D) 晴れだ

Q2. 「ご都合はいかが___か？」 (a polite business inquiry) Which fits the blank?

(A) です　(B) でしょう　(C) ですか　(D) だろう

Q3. 「明日の会議、田中さんも来る___？」 (confirming: he's coming too, right?) Which fits the blank?

(A) だろう　(B) でしょう　(C) かな　(D) かもしれない

Q4. 「彼はおそらく合格する___。」 (He will probably pass) Which is most appropriate?

(A) かもしれない　(B) でしょう　(C) ね　(D) よ

Q5. Which of the following is a correct polite question form?

(A) いつ来るだろうか

(B) いつ来るでしょうか

(C) いつ来ますでしょう

(D) いつ来るでしょう（falling tone）

Answer Explanations

1. (B) 晴れ ── noun 「晴れ」 + でしょう. The plain verb form is also OK (晴れるでしょう works too), but 「晴れでしょう」 (noun form) is the most common phrasing in weather forecasts.

2. (B) でしょう ── polite business questions use でしょうか: いかがでしょうか.

3. (B) でしょう ── でしょう (rising tone) = confirming "right?"; it is more polite and formal. ね also works, but でしょう is more formal.

4. (B) でしょう ── おそらく pairs with でしょう to express a moderate-to-high degree of conjecture. かもしれない is too low a degree; ね/よ are not conjecture.

5. (B) いつ来るでしょうか ── polite question: verb plain form + でしょうか. (A) だろうか is colloquial/archaic; (C) 来ますでしょう doubles up the polite form.