I think
Very similar to 'Creo que', but can imply a more active thought process. Use it when you've given something more consideration.
Means 'It seems to me that...'. Use this to express an opinion based on perception or feeling, making it sound a bit softer.
A slightly more formal way to say 'I think', translating to 'I opine that...'. Good for expressing a clear, stated opinion.
I think it's going to rain later.
I think this is the best restaurant in the city.
Where is Ana? It seems to me she's in the office.
I think the bus arrives at five.
'Creo que' and 'Pienso que' are standard and understood everywhere in the Spanish-speaking world.
In addition to the standard phrases, 'Se me hace que...' is a very common informal alternative for 'It seems to me that...' or 'I get the feeling that...'. For example, 'Se me hace que no van a venir' (I get the feeling they aren't coming).
A very common colloquialism is 'Para mí que...', which is used to introduce an opinion. For example, 'Para mí que la película es aburrida' (In my opinion, the movie is boring).
Usage is very similar to Latin America, with 'Creo que' and 'Pienso que' being the most common. The verb 'opinar' ('Opino que...') might be slightly more frequent in formal or semi-formal discussions.
Usage is standard. 'Creo que', 'Pienso que', and 'Me parece que' are all frequently used in daily conversation.
Using 'pensar que' for 'to think about'. — To say you are thinking *about* someone or something, you must use 'pensar en'. For example, 'Pienso en mis vacaciones' (I'm thinking about my vacation). Using 'Pienso que...' means you are stating an opinion: 'Pienso que las vacaciones son importantes' (I think that vacations are important).
Using the subjunctive mood after 'Creo que'. — When you state a belief affirmatively with 'Creo que', you use the indicative (normal) mood. Incorrect: 'Creo que sea una buena idea.' Correct: 'Creo que es una buena idea.' The subjunctive is only used when the phrase is negative ('No creo que sea...').
Always including 'Yo' before 'creo'. — In Spanish, the verb ending tells you who is speaking. 'Creo' already means 'I believe/think'. Saying 'Yo creo que...' is not wrong, but it adds emphasis. Learners often overuse 'yo', which can sound unnatural. Only add it if you need to contrast your opinion with someone else's.