かもしれない
Expresses that something is possible but uncertain: 'may,' 'might,' 'perhaps.' The speaker is not confident and allows that the opposite could also be true.
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A neutral way to say something might be the case, used in both conversation and writing. The polite form かもしれません suits polite speech, while the shortened かも is casual. It conveys relatively low certainty. Unlike でしょう/だろう, it expresses weaker confidence, and unlike ようだ or らしい, it does not rely on evidence or hearsay.
Do not put だ between a noun or な-adjective stem and かもしれない; say 雨かもしれない, not 雨だかもしれない.
Note that かもしれない signals low certainty, so it sounds odd for things the speaker is sure of or strongly believes.
Note that the shortened かも is casual and should be avoided in formal speech or writing.
- でしょうN5「でしょう」 also expresses conjecture, but with higher certainty than 「かもしれない」— the speaker is fairly confident. It can also be said with a rising intonation to seek confirmation from the listener ("..., right?"), a use 「かもしれない」 does not have.
- だろうN5When expressing conjecture, the two attach the same way and are interchangeable, but 「だろう」 carries more confidence, close to "probably." 「だろう」 can also use rising intonation to seek confirmation, and it is plain form—use 「でしょう」 in polite situations.
- はずだN4「はずだ」 is a confident inference based on reasons or common sense, far more certain than 「かもしれない」. Attach 「の」 after nouns and 「な」 after な-adjective stems. It can also express an original expectation, as in 「はずだった」.
- ようだN4「ようだ」 makes inferences based on what the speaker has seen or experienced firsthand; 「かもしれない」 merely indicates possibility, without emphasizing evidence, and carries lower confidence. 「ようだ」 takes 「の」 after nouns and 「な」 after な-adjectives; its figurative (metaphorical) use cannot be replaced with 「かもしれない」.
- らしいN4「らしい」 is based on hearsay or external signs and can mean "I heard that...". Replacing it with 「かもしれない」 still expresses conjecture, but no longer conveys the source of the information. 「らしい」 attached to a noun to mean "typical of / befitting..." cannot be replaced.
- に違いないN3「に違いない」 expresses the speaker's strong, evidence-based conviction, far more certain than 「かもしれない」; its polite form is 「に違いありません」. The two attach the same way, directly to stems or nouns. They are interchangeable, but the tone becomes one of strong assertion.
かもしれない expresses mere possibility with low certainty, whereas でしょう/だろう show a more confident guess, はずだ an expectation based on reasoning, and に違いない strong conviction. ようだ and らしい are judgments based on observed evidence or hearsay, which かもしれない does not require.
