Do I say "pensar EN" or "pensar A"

[Yoodle15]

Are both prepositions applicable depending on the context?

[Rusty]

Yes, and there are other prepositions. It's also possible to have no preposition. Each variant means something different.

pensar a = remember, reminisce over
pensar de = think about (opinion), be of the opinion about
pensar en = think about (process of thought), think of, have in mind
pensar sobre = think over, think about
pensar = think about (consideration), think (belief), plan to/intend to

[Yoodle15]

Gracias!

[ROBINDESBOIS]

Pensar is followed by en almost always. I dont know where Rusty got that information from, but I never heard it.

[AngelicaDeAlquezar]

I have never heard "pensar a" (unless there is an idiomatic expression following, like "a ratos", "a fuerzas"/"a la fuerza", "a color(es)"... to give some sort of poetic idea). Although there may well be some regional use.

I agree with the rest of Rusty's statements.

[Rusty]

Hmmm. I can no longer find supporting evidence for the 'pensar a' option, except in cases like those mentioned in the post above and a few others, but none of them mean to 'reminisce over'. Retiro lo dicho.

[Don José]

"Pensar a X", being X a person, is sometimes used as "think about his/her work". For example: pensar a Marx.
However, it is not used in everyday speaking situations.

[AngelicaDeAlquezar]

Ah, of course! Thank you, Don José, for the reminder.

·Pensar a Kant desde la perspectiva de Heidegger. -> To consider Kant's work from Heidegger's views.

[PoquitaChapina]

I always same "pensando en" if that helps. I know it is correct because I hear native Spanish speakers say that. For example, "ahora mismo, estoy pensando en mi matemáticas".

Also, when my boyfriend is feeling romantic, he tells his me "estoy pensando en ti"