目錄
Japanese has many grammar patterns for expressing ideas such as “might,” “probably,” and “should,” but two of the forms learners most often struggle with are 「〜かもしれない」 and 「でしょう」. In Chinese translation, both are often rendered as “可能,” “大概,” or “吧,” but in the mind of a native Japanese speaker, these two forms represent very different levels of confidence and very different speaking nuances.
The main reason these two patterns are easy to confuse is that Chinese translation tends to flatten the differences in nuance. Learners often focus only on “whether this will happen or not,” while Japanese grammar places more emphasis on “how much responsibility the speaker is willing to take for what they are saying.” When using 「〜かもしれない」, the speaker leaves themselves a great deal of room, so the tone sounds cautious and simply acknowledges that something is possible. By contrast, 「でしょう」 sounds noticeably more confident and is usually used when the speaker already has some clues or experience that support a relatively firm judgment.
What Are the Uses of 「〜かもしれない」 and 「でしょう」? Core Functions and Attachment Rules
Attachment Rules
| What It Attaches To | 〜かもしれない | でしょう |
| Verb | 行くかもしれない | 行くでしょう |
| い-adjective | 高いかもしれない | 高いでしょう |
| な-adjective | 静かかもしれない | 静かでしょう |
| Noun | 雨かもしれない | 雨でしょう |
「〜かもしれない」 attaches to the plain form. Its polite form is 「〜かもしれません」, while in conversation it can be shortened to 「かも」. 「でしょう」 is the polite form of 「だろう」 and can be used both for conjecture and for seeking agreement. Readers first need to determine whether a sentence expresses a “low-confidence conjecture” or a “soft confirmation.”
Usage of 「〜かもしれない」｜Expressing a Low-Confidence Possibility
The key idea behind 「〜かもしれない」 is “this possibility cannot be ruled out.” It does not necessarily mean that the speaker strongly believes the statement. Rather, it simply introduces one possible scenario into the sentence. In everyday conversation, it is often used to avoid sounding too definite, and it can also make advice sound softer.
- Example: 明日は雨が降るかもしれません。
Kana: あしたはあめがふるかもしれません。
Translation: It might rain tomorrow.
This sentence only leaves open the possibility of rain; it does not say that rain is highly likely. - Example: この道は少し遠回りかもしれない。
Kana: このみちはすこしとおまわりかもしれない。
Translation: This route might be a bit of a detour.
This sounds natural while traveling and carries the nuance of “I’m not sure, but it feels that way.” - Example: 彼はまだ駅に着いていないかもしれない。
Kana: かれはまだえきについていないかもしれない。
Translation: He might not have arrived at the station yet.
The sentence does not make a strong assertion; it simply proposes a possibility based on the current situation.
Usage of 「でしょう」①｜Expressing a Conjecture Based on Evidence
「でしょう」 usually indicates that the speaker has a certain degree of confidence. That confidence may come from a weather forecast, past experience, visible clues, or a judgment based on common sense. It is more assertive than 「〜かもしれない」, but softer than a direct statement with 「です」.
- Example: この雲なら、午後は雨でしょう。
Kana: このくもなら、ごごはあめでしょう。
Translation: Looking at these clouds, it’ll probably rain this afternoon.
Here, 「でしょう」 is based on the visible sky, so the judgment carries more confidence than 「かもしれない」. - Example: 週末の浅草は混んでいるでしょう。
Kana: しゅうまつのあさくさはこんでいるでしょう。
Translation: Asakusa will probably be crowded on the weekend.
This is a natural conjecture based on common knowledge and experience. - Example: この説明なら、初めての人にもわかるでしょう。
Kana: このせつめいなら、はじめてのひとにもわかるでしょう。
Translation: With this explanation, even someone seeing it for the first time should understand.
「でしょう」 leaves some room for uncertainty while still conveying a fair amount of confidence.
Usage of 「でしょう」②｜Expressing Soft Confirmation
When 「でしょう」 is said with rising intonation at the end, it often becomes a confirmation meaning something like “right?” In this case, it is not merely conjecture; the speaker is expecting the listener to agree. This usage is very different from 「〜かもしれない」 and the two cannot be interchanged.
- Example: このケーキ、おいしいでしょう。
Kana: このケーキ、おいしいでしょう。
Translation: This cake is delicious, right?
The speaker expects the listener to agree, so the tone is one of soft confirmation. - Example: 京都の夜は静かでしょう。
Kana: きょうとのよるはしずかでしょう。
Translation: Nights in Kyoto are quiet, right?
If the sentence ends with rising intonation, it becomes an invitation for the listener to share their impression. - Example: この席から花火がよく見えるでしょう。
Kana: このせきからはなびがよくみえるでしょう。
Translation: You can see the fireworks well from this seat, right?
This is not a low-confidence conjecture, but a confirmation of the situation in front of the speaker.
What Is the Difference Between 「〜かもしれない」 and 「でしょう」?
| Comparison | 〜かもしれない | でしょう |
| Level of confidence | Low to medium | Medium to high |
| Core nuance | It is possible, but the judgment is reserved | It is probably so, based on some evidence |
| Common translations | might, maybe, perhaps | probably, should, right |
| Spoken contraction | かも | でしょ |
| Common mistake | Overusing it can make the speaker sound unsure | Using it for a low-probability guess can sound too certain |
▌When Probability Is Low, 「〜かもしれない」 Is More Natural
❌ Unnatural: 財布はホテルにあるでしょう。
(If this is only a guess, the tone is too certain.)
✅ Correct: 財布はホテルにあるかもしれません。
The location of a lost item is only a possibility, so 「〜かもしれない」 better matches the nuance of withholding judgment.
▌When There Is Clear Evidence, 「でしょう」 Is More Natural
❌ Too weak: この行列なら、人気店かもしれません。
✅ Natural: この行列なら、人気店でしょう。
There is already a visible clue—the line of people—so 「でしょう」 can express a conjecture based on that evidence.
「〜かもしれない」 and 「でしょう」 in Japanese Conversation: Conjecture in Travel Situations
Travel is one of the situations where conjecture is especially useful, particularly when talking about weather, transportation, crowds, and reservations. Japanese speakers often avoid making absolute statements, but the amount of uncertainty they leave changes the way a sentence sounds. 「〜かもしれない」 leaves more room, while 「でしょう」 makes the advice sound more like a judgment based on experience.
▌Situation ①｜Deciding Plans Based on the Weather
A：午後は雨が降るかもしれませんね。
ごごはあめがふるかもしれませんね。
It might rain this afternoon.
B：そうですね。この雲なら、早めに移動したほうがいいでしょう。
そうですね。このくもなら、はやめにいどうしたほうがいいでしょう。
Right. Looking at these clouds, we should probably move earlier.
📌 Grammar Point: A first presents a possibility, while B makes a judgment based on the clouds. The two forms express different levels of certainty.
▌Situation ②｜Seeing a Line Outside a Restaurant
A：この店、予約しないと入れないかもしれません。
このみせ、よやくしないとはいれないかもしれません。
We might not be able to get into this restaurant without a reservation.
B：この行列なら、かなり人気の店でしょう。
このぎょうれつなら、かなりにんきのみせでしょう。
With a line like this, it’s probably a very popular restaurant.
📌 Grammar Point: 「入れないかもしれません」 leaves open a possibility, while 「人気の店でしょう」 is a judgment based on the visible crowd.
Cultural Notes:
- Japanese often uses conjectural expressions to leave room for uncertainty. This is not simply vagueness; it helps avoid presenting uncertain information as absolute fact.
- 「でしょう」 is common in service situations because it is softer than 「です」 while sounding more confident than 「かもしれない」.
- The spoken form 「でしょ」 often has a confirmatory feel and sounds natural among friends, while 「でしょう」 is generally safer in more formal situations.
How Should You Understand Japanese 「〜かもしれない／でしょう」 Compared with Korean 「-ㄹ지도 모르다／-겠어요」?
◆ Similar Grammar: Korean 「-ㄹ지도 모르다」 and 「-겠어요」
Korean 「-ㄹ지도 모르다」 is close to “might” or “maybe,” with a relatively strong sense of reservation. By contrast, when 「-겠어요」 is used for conjecture, it is closer to a judgment made on the basis of the situation.
- Example: 오후에 비가 올지도 몰라요.
Romanization: o-hu-e bi-ga ol-ji-do mol-la-yo
Translation: It might rain this afternoon.
The nuance is close to the Japanese 「雨が降るかもしれません」. - Example: 이 줄이면 맛집이겠어요.
Romanization: i ju-ri-myeon mat-ji-bi-ge-sseo-yo
Translation: With a line like this, it must be a popular restaurant.
The nuance is close to the Japanese 「人気店でしょう」.
◆ Core Difference from 「〜かもしれない／でしょう」:
Japanese clearly distinguishes reservation and judgment through 「かもしれない」 and 「でしょう」, while Korean adjusts the degree of certainty through sentence endings, intonation, and context.
At this point, it becomes clear that Japanese 「〜かもしれない」 and 「でしょう」 are not interchangeable versions of “maybe.” The choice depends on how much evidence the speaker has at that moment and how strongly they are willing to state their judgment. Use 「〜かもしれない」 when you want to be more cautious, and switch to 「でしょう」 when you have some evidence and want to give a more confident judgment or suggestion. Each form has its own role in conversation.
Common FAQs
「〜かもしれない」 indicates that something may happen or may be true. The speaker’s level of confidence is usually not high, making it suitable when they do not want to make a definite statement and only want to present a possibility.
「でしょう」 expresses a conjecture based on some degree of evidence and can also be used for soft confirmation. It is less definite than 「です」 but conveys more judgment than 「〜かもしれない」.
The main difference is the level of confidence. 「〜かもしれない」 leaves open a possibility, while 「でしょう」 expresses a more confident conjecture based on clues or common knowledge.
「かも」 is a shortened conversational form with a lighter, more casual tone. 「かもしれない」 is the full form, while 「かもしれません」 is the polite form.
「でしょ」 is the more conversational form and is often used among friends for confirmation or casual conjecture. 「でしょう」 is more polite and is suitable for explanations, service situations, and somewhat more formal conversations.