意味 & 使い方 (Meaning & Usage)
でしょう is the polite presumptive form of the copula です. While です states a factual certainty, でしょう allows you to express uncertainty, 推量 (conjecture), or a desire for agreement from the 相手 (listener).
The meaning of でしょう shifts based on your 抑揚 (intonation):
- Probability (Falling Intonation): This means "probably" or "I think it's likely." It suggests you are about 70-90% sure based on evidence. You will hear this constantly during a 天気予報 (weather forecast).
- Confirmation (Rising Intonation): This acts like an English tag question ("...right?" or "...don't you agree?"). Use this when you are fairly sure of a fact but want to soften your tone or invite the listener to agree.
Think of this grammar as a "polite buffer." Stating things too directly in Japanese can sometimes feel blunt or overly assertive. By using でしょう, you leave space for other opinions and maintain social harmony.
接続 & 形 (Structure & Formation)
Connecting words to でしょう is straightforward. It usually attaches to the 普通形 (plain form) of verbs and adjectives. However, there is one crucial rule: remove the だ from 名詞 (nouns) and な形容詞 (na-adjectives).
| 品詞 (Part of Speech) | 接続 (Connection) | 例 (Example) |
|---|---|---|
| 動詞 (Verb) | Plain Form + でしょう | 降る + でしょう |
| い形容詞 | Plain Form + でしょう | 寒い + でしょう |
| な形容詞 | Stem (No だ) + でしょう | 静か + でしょう |
| 名詞 (Noun) | Noun (No だ) + でしょう | 晴れ + でしょう |
For the past tense, use the plain past forms (e.g., 行った, 美しかった, 静かだった, 雨だった) before adding でしょう.
例文 (Example Sentences)
推量 (Probability)
明日は雨が降るでしょう。
ashita wa ame ga furu deshou.
It will probably rain tomorrow.
田中さんはもう駅に着いたでしょう。
tanaka san wa mou eki ni tsuita deshou.
Mr. Tanaka has probably already arrived at the station.
その試験はあまり難しくないでしょう。
sono shiken wa amari muzukashikunai deshou.
That exam probably won't be very difficult.
北海道は今寒いでしょう。
hokkaido wa ima samui deshou.
Hokkaido is likely cold right now.
確認 (Seeking Confirmation)
この料理は美味しいでしょう？
kono ryouri wa oishii deshou?
This food is delicious, isn't it?
京都は静かでしょう？
kyouto wa shizuka deshou?
Kyoto is quiet, isn't it?
昨日の映画は良かったでしょう？
kinou no eiga wa yokatta deshou?
Yesterday's movie was good, right?
日本の生活は楽しいでしょう？
nihon no seikatsu wa tanoshii deshou?
Life in Japan is fun, isn't it?
丁寧な意見 (Polite Opinions & Nuance)
それはちょっと無理でしょう。
sore wa chotto muri deshou.
That might be a bit impossible (a polite way to decline).
皆さん、お腹が空いたでしょう。
minasan, onaka ga suita deshou.
Everyone, you must be hungry (right?).
間違いやすい点 (Common Mistakes)
1. Adding "da" unnecessarily
❌ 雨だでしょう。
✅ 雨でしょう。
Students often try to keep the だ from the plain form. Since でしょう is already a polite version of the copula, adding だ is redundant and grammatically incorrect.
2. Describing your own certain plans
❌ 私は明日学校へ行くでしょう。
✅ 私は明日学校へ行きます。
Avoid using でしょう for your own planned actions. Using it makes you sound like you are guessing about yourself, which feels unnatural to native speakers. Only use it for yourself if you are speculating about a future feeling, such as "I'll probably be tired."
3. Confusing Intonation
If you use a falling intonation while asking for agreement, you may sound cold or robotic. Conversely, using a rising intonation for a weather report makes it sound like you are unsure of your own data, which is unprofessional for a forecaster.
文化 的な注意 (Cultural Notes)
In Japanese conversation, でしょう helps maintain reserve. By using a presumptive ending, you avoid being dogmatic. This allows your listener to hold their own opinion, which is a key part of 丁寧 (polite) interaction.
Weather forecasts almost exclusively use でしょう. Since the weather is never 100% certain, the meteorological agency uses this grammar to "predict" rather than "promise." This linguistically protects them if the forecast is slightly off.
関連する文法 (Related Grammar)
- だろう — The casual/plain version of でしょう, mostly used by men.
- かもしれません — Means "might"; indicates a lower probability (around 50%) than でしょう.
- ～と思います (to omoimasu) — "I think"; focuses on the speaker's personal opinion.
- はずです — "Expected to"; used when there is a strong logical reason to believe something.
Related Grammar Points
- です — Polite Copula (Is/Am/Are) (Grammar N5)
- Understanding はずだ: Expressing Logical Expectations (Grammar N4)
- Using かもしれない (kamoshirenai) to Express Possibility (Grammar N4)
- か — Question Marker (Grammar N5)
- てください — Please Do (Grammar N5)
- ましょう — Let's Do Something Together (Volitional Polite) (Grammar N5)
JLPT 試験のコツ (JLPT Tips)
For the JLPT N4 listening section, listen closely to the end of the sentence. A rising pitch means the speaker is seeking an opinion. A falling pitch indicates they are stating a probability.
In the reading section, watch for keywords like 多分 (probably) or きっと (surely). These words often pair with でしょう. Finally, remember the "No だ" rule for nouns and na-adjectives, as this is a frequent trap in grammar multiple-choice questions.