Para is used to express:
use or destination (for), purpose (in order
to); point of future time (for, by) and
to be about to (estar para + infinitive.)
La carta es para Concha.
The letter is for Concha.
Estudia para aprender. He studies
in order to learn.
Lo tendré para el martes. I
will have it by Tuesday.
Juan está para salir. John
is about to leave.
Por is used to express:
a place through or along which; expressions
of time (in, during, at); exchange, price
(for); unit of measure (by, per); way or
means (by); because of, on account of, for;
to go for, to send for; on behalf of, for
the sake of; motive, reason. It is
also used after a passive verb to indicate
the agent (by) and estar por + infinitive
indicates what remains to be done or to
be in favor of.
por el pueblo through
the town
por la mańana in the morning
Pagó un peso por el libro. He
paid a dollar for the book.
Se vendre por libras. It's
sold by the pound.
Voy por tren. I'm going by
train.
Voy por Alicia. I'm going for
Alice.
Voté por Juanita. I voted for
Juanita.
Fue escrito por Cervantes. It
was written by Cervantes.
La carta está por escribir. The
letter is yet to be written.
Estoy por escribirla. I am
in favor of writing it.
Pero (but) usually follows
an affirmative expression, but may follow
a negative statement if the verb of the
first clause is repeated, or if another
verb follows.
Bebe lecho pero no bebe café.
He drinks milk, but he does not
drink coffee.
Sino (but) is only used
in negative sentences of contrasting statements
when the verb of the first clause is understood
but not repeated.
No bebe café sino leche.
He does not drink coffee, but
milk.
