Time and Place
The Spanish preposition "por" is often used when referring to time and place. It also vaguely expresses local and temporal relationships.
- ir por la calle (to go by the street)
- por aquellos días (in those days)
- por abril (around April)
When the term is well defined, the meaning becomes more precise. This can be seen in the following example:
- entrar por la puerta (to enter through the door)
Agent of the Passive, Medium, and Mode
The Spanish preposition "por" is also used when we want to introduce the agent of a passive action.
- ha sido arrestado por la policía (he has been arrested by the police)
- fue programado por mi tío (it was programmed by my uncle)
The preposition "por" also expresses the medium through which an action is carried out. Observe the following two examples:
- oir el noticero por la radio (to hear the news on the radio)
- hablar por teléfono (to talk on the telephone)
In terms of mode, the preposition "por" forms adverbial and conjunctive phrases:
- por fín (at last)
- por lo general (in general)
- por más que (even though, despite)
Substitution, Cause, and Imminence
This preposition, "por," is often used to express an action that is carried out by a subject on behalf of someone else. Look at these examples:
- salúdale por mí (say hello to him on my behalf)
- trabajo por mi padre cuando se enferma (I work in place of my father when he gets sick)
- hazlo por mí (do it for me, do it on my behalf)
Finally, the preposition "por" is utilized to express the cause of an action. For example:
- Ayuda, por el amor de Dios (For the love of God, help)
- Por haber llovido mucho el camino está cerrado (The way is closed on account of it having rained so much)
With the expression "me sacrificio por tí," we mean "por tu causa," or "for your cause," whereas by "me sacrificio para tí," we mean "on your behalf" or "for your benefit." This difference is often confused by English speakers.
The preposition "por" has one more use. We can employ it to express doubtful disposition toward a future action. In other words, we can use it to say that we are in the process of getting ready to do something but the action has not yet come to pass.
- estoy por salir (I am getting ready to go out)
- estoy por regresar (I am getting ready to come back)
- Estamos por comer (We are getting ready to eat)
*This same construction with the preposition "para" signifies the imminence of an action, as in the example: estoy por salir (I am about to go out).