Grammar JLPT Level N4 - Lesson 6

Structure of と思(おも)う:

Verb + と思(おも)う⁽¹⁾
［い］Adjective + と思(おも)う⁽¹⁾
［な］Adjective + だ + と思(おも)う⁽¹⁾
Noun + だ + と思(おも)う⁽¹⁾

⁽¹⁾ と思(おも)っている

Details about と思(おも)う:

To express that you 'think' something in Japanese, the common expression と思(おも)う is regularly used. As you can probably guess, this is just a combination of the particle と, plus the う-Verb 思(おも)う. とおもう can be used after any verb, い-Adjective, な-Adjective, or noun, but will require だ after a noun or な-Adjective.

ごめん、ちょっと遅(おく)れると思(おも)う。
Sorry, I think I'm going to be a little late.
その言(い)い方(かた)は酷(ひど)いと思(おも)うよ。
I think the way you said that was harsh.
俺(おれ)はあの人(ひと)が綺麗(きれい)だと思(おも)う。
I think that person looks pretty.
これはフランス語(ご)だと思(おも)う。
I think this is French.

Although this structure usually requires だ after nouns and な-Adjectives, it is often omitted in casual speech.

私(わたし)は日本(にほん)が安全(あんぜん)と思(おも)う。
I think Japan is safe. (Ungrammatical Japanese, but quite common)

と思(おも)う

Usage Notes for と思(おも)う:

If you want to express what somebody else is thinking, と思(おも)っている will be used. This is due to と思(おも)う having a sense of 'permanence', and thus not something that the speaker could know about another person. と思(おも)っている can also be used to express your own thoughts when they are currently happening.

ジェームスは自分(じぶん)が賢(かしこ)いと思(おも)っている。
James thinks he is smart.
来年(らいねん)に新(あたら)しいオートバイを買(か)いたいと思(おも)っている。
I am thinking that I want to buy a new motorcycle next year.