Grammar
N4 verb-grammar

I think that 〜と思う

Meaning

States an opinion or belief — "I think that ~". The quotative particle と marks the thought, and 思う reports it.

Formation

Notes

The clause before と is ALWAYS plain form, even when 思います is polite: 高いと思います (NOT ×高いですと思います). To negate an opinion, negate the inner clause, not 思う — Japanese says 来ないと思います ("I think he won't come") far more naturally than 来ると思いません. Use 〜と思っています for a settled, held-over-time belief, especially about someone else.

Examples

I think it will rain tomorrow.

Breakdown
tomorrow (topic) rain (subject) to fall (plain form before と) (quotative) I think

I think this book is interesting.

Breakdown
this book (topic) interesting (plain, no です) (quotative) I think

I don't think he'll come. (negate the inner clause, not 思う)

Breakdown
he (topic) does not come (quotative) I think

I think Tanaka-san is a student. (noun takes plain だ before と)

Breakdown
Tanaka-san (topic) student is (plain copula — required before と) (quotative) I think

What do you think? (NOT ×何を思いますか)

Breakdown
how / what do you think?

I'm thinking of working in Japan in the future. (〜と思っている = a held belief)

Breakdown
I (topic) in the future Japan (place of action) want to work (quotative) have been thinking

⚠️ Often confused with

Say that 〜と言う

Reports speech — "(someone) says/said that ~". The same quotative と, this time with 言う....

Called / named 〜という

Introduces a name or label the listener may not know — "a ~ called ~".

Casual quotation 〜って

The spoken stand-in for と / という — reports speech, names a topic, or asks what somethin...

I hear that 〜ということだ

"I hear that ~"; also "that means ~".

Speaking of 〜といえば / 〜というと

"Speaking of ~", "when you say ~".