por y para

A. PARA (destination or purpose):
1. Direction toward a destination or goal:
Salgo mañana para Madrid.
Vamos para la oficina.
I am leaving tomorrow for Madrid.
We're going to the office.
2. Purpose, use, goal or destination toward a recipient:
taza para café coffee cup
Había espacio para todos.
Estudié medicina para ayudar.
Practican para mejorar.
Compró estos libros para ti.
Trabaja para la OTAN.
llantas para la nieve snowtires
There was room for everybody.
I studied medicine in order to help.
They practice to improve.
He bought these books for you.
She works for NATO.
3. Time limit or deadline:
Hay que hacerlo para el lunes. It needs to be done by/for Monday.
4. Comparison against the normal expectation:
Tiene una gran población para un país tan pequeño.
It has a large population for such a small country.
Para ser extranjero, habla muy bien el idioma.
For a foreigner, he speaks the language very well.
5. Opinion: "To me..."
Para mí, la política es interesante.
La vida es valiosa para cualquiera.
To me, politics is interesting.
Life is valuable to anyone.
Use para in Spanish whenever you could use "in order to" in English. For example:
(in order) To improve, people have to do this.
I do it (in order) to have fun.
I do it to improve.
BUT:
It's not easy to improve this.
(you couldn’t insert “in order to” here)
Para mejorar, hay que hacer esto.
Lo hago para divertirme.
Lo hago para mejorar.
No es fácil mejorar esto.
B. POR (motivation or substitution):
1. Exchange, substitution, rate, correspondence (per):
Te doy cinco dólares por el libro.
Gracias por todo.
No me tomes por idiota.
a veinte kilómetros por hora
el diez por ciento
$3 por galón.
I'll give you five dollars for the book.
Thanks for everything.
Don't take me for an idiot.
twenty kilometers an hour
ten percent
$3 per gallon
2. a. Cause, reason, or motive of an action (because of, to fetch):
Lo merece por su dedicación.
Fuimos al mercado por pan.
Te quería por tu honestidad.
No jugaron por la lluvia.
He deserves it for (because of) his dedication.
We went to the store for bread.
I loved you for your honesty.
They didn’t play because of the rain.
b. On behalf of, for the sake of, in favor of, out of:
Lo hice por el dinero. I did it for the money.

No lo hago por ti.
Se preocupan por mí.
Luchan por la independencia.
Trabajaba por la paz mundial.
A menudo me pregunta por ti.
I'm not doing it on your account.
They worry about me.
They fight for independence.
She worked for world peace.
He often asks about you.
3. Duration in time (often omitted):
Estuvo en México (por) seis semanas.He was (stayed) in Mexico for six weeks. During the morning,
evening, or afternoon: Trabajaba por la mañana.He used to work in the morning.
4. Movement through a place:
Iba por la calle cuando...
Pasa por mi oficina.
Vamos a pasear por el parque.
I was going down the street...
Drop by my office.
We are going to take a walk through/by the park.
5. Agent in a passive phrase (by):
Fue escrito por ella.
Está afectada por la noticia.
It was written by her.
She's affected by the news.
6. Means of transportation or communication (by)
El paquete llegó por avión.
Llámame por teléfono.
The package arrived by plane.
Call me on the telephone.
7. In a large number of idiomatic expressions:
por fin
por ejemplo
por desgracia
por supuesto
por eso
por aquí
finally, at last
for example
unfortunately
of course
that's why
around here
por lo menos
por favor
por primera vez
por casualidad
por otra parte
por lo tanto
at least
please
for the first time
by (any) chance
on the other hand
therefore
The questions ¿para qué? (for what purpose?) and ¿por qué? (for what reason or motive?) can
give you clues on choosing the appropriate preposition. Both prepositions will often be
grammatically correct, but they would convey different meanings:
Recibimos dinero por la investigación.
I got money from the research (done). [exchange]
Recibimos dinero para la investigación.
I got money for the research (to do). [purpose]
Compré esto por ti.
I bought this because you wanted me to. [motive]
Compré esto para ti.
I bought this to give it to you. [destination]