Tro, Tenke, Synes

In English we can say "I think" to cover any cognitive ability, any opinion or any expression of knowledge of facts. In Norwegian, each of these situations has it's own verb. This is often troublesome to English speakers. Study these examples.
å tro ( to think, to believe)(facts can be verified)

Jeg tror på deg. (I believe in you)
Jeg tror det er kaldt ute. (I think it's cold outside. I haven't been out there.)
Jeg tror han kommer i morgen. (I think he's coming tomorrow.)

å tro/ tror/ trodde/ har-hadde trodd

å tenke (to think, the act of thinking)

Jeg tenker på deg. (I am thinking of you.)
Jeg tenker saken over. (I am thinking about the matter)
Jeg tenker ofte om ferien vår. (I often think of our vacation.)

å tenke/ tenker/ tenkte/ har-hadde tenkt

å synes (to think, expressing opinion) Jeg synes du er pen. (I think you are pretty)
Jeg synes det er kaldt ute. (I think it's cold outside. I have been out there. It is my opinion.)
Jeg synes han er en tosk. (I think he's a fool).

å synes/ synes/ syntes/ har-hadde synes