Por vs. Para
Two prepositions, two very different jobs
Both por and para can translate as 'for' in English, but they answer different questions. Para points forward — to a destination, a purpose, a deadline. Por points sideways or backward — to a cause, a means, an exchange.
Use para for
Purpose ('para aprender'), destination ('para Madrid'), deadlines ('para el lunes'), recipients ('para ti'), and opinions ('para mí').
Use por for
Cause or motive ('por amor'), exchange ('te cambio el mío por el tuyo'), duration ('por dos horas'), means ('por avión'), and movement through ('caminé por el parque').
Ejemplos
"Este regalo es para ti."
This gift is for you.
Recipient — para.
"Gracias por el regalo."
Thanks for the gift.
Cause/motive — por.
"Estudio para ser médico."
I study to become a doctor.
Purpose — para.
"Viajamos por España."
We travel through Spain.
Movement through — por.