Japanese Grammar Bank

HOW TO USE ~だろう & ~と思う

There are several different expressions to express conjecture and speculation in Japanese, such as ~だろう, ~と思うand ~かもしれない.

This article will help you to learn and use such expressions in your daily life.

USING ~だろ

だろう (darō) is one way to express speculation based on opinions and guess.

だろう is used when the speaker is pretty sure about his conclusion but it’s not based on solid evidence.

だろう comes after nouns, adjectives, and verbs in both positive and negative forms.

PATTERN

Noun / な-adjective / い-adjective / Verb + だろう

彼は学生だろう。I assume he is a student.
あの人はアメリカ人だろう。I assume that person is American.
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彼女は歌が下手だろう。I assume she is not good at singing.
明日のテストはたいへんだろう。I assume tomorrow’s exam is the difficult one.
彼女は若いだろう。I assume that she is young.
来週は寒いだろう。I assume it’s going to be cold next week.
父は駅まで歩くだろう。I assume that my father will walk till the station.
彼は来年車を買うだろう。I assume that he is going to buy a car next year.

ALTERNATIVE

PATTERN

Noun / な-adjective / い-adjective / Verb + でしょう

次の総理大臣はあの人でしょう。I guess next prime minister will be that person.
明日は雪でしょう。I assume it will snow tomorrow.
明日の野球の試合はうちの学校が勝つでしょう。I assume my school team will win the baseball match tomorrow.

USING ~と思う

と思う can be used to express your thoughts and ideas as speculation.

This expression is a combination of と and 思う, and it comes after nouns, adjectives, and verbs in both positive and negative forms.

You just need to add ~と思う/~と思います at the end of sentence.

PATTERN

Noun / な-adjective / い-adjective / Verb +と思う

あの人は親切だと思います。I think that person is kind.
この説明はとても複雑だと思います。I think this explanation is very complicated.
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このケーキは美味しいと思います。I think this cake is delicious.
母は嬉しいと思います。It seems like my mother is happy.
来年は旅行に行くと思います。I think I am going to vacation next year.
この本は読まないと思います。I think I’m not going to read this book.

USING ~かもしれない

かもしれない can be used to express conjecture, but this expressions shows you don’t have much confidence in your assumption.

This is an expression for conveying a low level of certainty.

〜かもしれない always follows the plain form.

PATTERN

Noun / な-adjective / い-adjective / Verb + かもしれない

彼は日本人かもしれない。He may be Japanese.
この仕事はたいへんかもしれない。This work may be hard.
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来週はひまかもしれない。I may be free next week.
明日は暑いかもしれない。Tomorrow may be hot weather.
友達の結婚式で歌うかもしれない。I may sing in my friend’s wedding.
明日家族で動物園に行くかもしれない。We may be going to zoo tomorrow as family.

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FAQs

When should I use だろう instead of と思う for speculation?

Use だろう when making an educated guess or assumption, especially in casual or semi-formal contexts. と思う is more commonly used for expressing a personal opinion or thought.

Is だろう polite enough for formal situations?

だろう can be used in informal and semi-formal situations. However, in formal contexts, it’s better to use でしょう, which is the polite form of だろう.

Can I use だろう and と思う together?

Yes, it’s possible to combine them to add a nuance of both assumption and personal thought. For example, 行くだろうと思う can be used to mean “I think they will probably go.”

What’s the difference between using だろう and using かもしれない?

だろう implies a stronger sense of likelihood, while かもしれない expresses a weaker possibility, closer to “might” or “maybe.”

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