〜と思う
Giving an opinion or thought: I think that…machine translation
FormationPlain form + と思う (nouns and な-adjectives + だと思う)
〜と思う is the most common way in Japanese to state an opinion or a guess: 雨が降ると思います (I think it will rain). The clause before と is always in plain form; with nouns and な-adjectives, remember to keep だ: 便利だと思います.
思う in the present tense is only used for the speaker's OWN thoughts. To talk about someone else's thoughts, or an intention you've been nurturing for a while, use 〜と思っています: 妹は日本で働きたいと思っています.
The negative usually goes in the clause, not on 思う: 来ないと思います (I think they won't come) is more natural than 来ると思いません. When you want to make a guess without stressing "this is my opinion," you can use だろう・でしょう instead.
Examples
明日は雨が降ると思います。
I think it will rain tomorrow.
日本の生活は便利だと思います。
I think life in Japan is very convenient.
妹は日本で働きたいと思っています。
My younger sister wants to work in Japan.