How to tell them apart
The core contrast is certainty level: でしょう/だろう expresses a confident guess with moderate probability, while かもしれない expresses genuine uncertainty, acknowledging a real possibility that could go either way. Swapping them feels off because かもしれない downplays what you're fairly sure of, and でしょう overstates what you're unsure about. For instance, 雨が降るでしょう sounds like a weather forecast, whereas 雨が降るかもしれない sounds like a mere possibility.
- だろう Use でしょう/だろう when you lean toward a likely outcome without hard evidence.
- かもしれない Use かもしれない when you genuinely can't tell and want to flag a real possibility.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| だろう darou | Likely so; I suppose | N4 |
| かもしれない kamoshirenai | might; possibly; perhaps | N4 |
だろう darou
Likely so; I suppose
だろう expresses the speaker's guess that something is likely true, like probably or I suppose, when the outcome is uncertain. It attaches to the plain form, as in 降るだろう, 高いだろう, and 休みだろう, with だ dropped before it for nouns and na-adjectives, while でしょう is the polite equivalent used in formal speech. Avoid using it for confirmed schedules or known facts, and keep the hedging sense rather than a certain will.
-
この車、高いんだろうな。
This car is probably expensive.
-
明日は雨が降るだろう。
It will probably rain tomorrow.
かもしれない kamoshirenai
might; possibly; perhaps
かもしれない expresses uncertain possibility, like might or perhaps, when the speaker is not sure if something is true or will happen. It follows the plain form of verbs and i-adjectives, as in 行くかもしれない or 高いかもしれない, and follows nouns and na-adjectives directly, as in 病気かもしれない or 静かかもしれない. For past possibility, use だったかもしれない, as in 病気だったかもしれない. It sounds conversational and uncertain, so avoid it for stating facts with confidence.
-
金持ちかもしれないがけちだ。
He may be rich, but he is stingy.
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オーストラリアに行かなきゃいけないかもしれないんだ。
I may have to go to Australia.
だろう and かもしれない are both JLPT N4 grammar points that Japanese learners often mix up. This page compares them side by side on meanings, usage and example sentences, so you can tell them apart.