[verb (plain form)] + と思う
[i-adj (plain form)] + と思う
[na-adj] + だ + と思う
[noun] + だ + と思う
Note: The quoted clause before と can be in any tense/polarity (e.g., ~ない、~た、~なかった). With volitional form (~よう/~おう + と思う) → "I think I will…" (speaker's intention).
~と思う expresses thoughts, opinions, or guesses about something in present, past, or future contexts.
Present Opinions:
Past Opinions:
Negative Opinions:
Future Assumptions: