"Fuimos al mercado por pan." Why not para?

Question

This link summarizes por and para usage rules and lists the following sentence under por in the category "cause, reason, or motive of an action".

Fuimos al mercado por pan

Why isn't para acceptable here? Para deals with purpose and objectives, no? It seems like there's a lot of overlap between a motive of an action and the purpose section of para. In the sentence, I think bread could be both the purpose and motivation. Could I get clarification on this?

Thank you.

Answer 1

Prepositions are, in my view, the most idiomatic words in the language.

In Spanish, we use:

• ir por algo (go for something)

to mean that you go somewhere to look for or get something.

However, if instead of a noun we use a verb, "para" (also "a") will be required:

• Fuimos al mercado por pan.
• Fuimos al mercado para comprar pan / a comprar pan.

Answer 2

Here are some use cases for (IR) POR/PARA.

ir por(v+prep) = to go for, go to fetch, buy or get

• I went out for(=to try to get/to try to buy) some bread (Fui/Salí por pan)

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por = for, about (FEELINGS)

• What I feel for you(Lo que siento por ti)
• I'm still a bit sorry about you(Bueno igual me da un poco de lata/pena por ti)
• I think that I have always felt something special for you(Creo que siempre he sentido algo especial por ti)

por = to, for, in favor of(For your own good)

• He's the one who did this to you(Él es el único que hizo esto por ti)
• I'd do anything for you(Haría cualquier cosa por ti)

por = for, in the stead of, on behalf of (when someone does something for you)

• She did your job for you(Hizo el trabajo por ti)

por = through, because of, on account of, for (MOTIVATIONS)(INDICATING CAUSE OR REASON)

• Because of her love for animals, he wants to be a veterinarian(Por su cariño por los animales quiere ser veterinario)

por = about(CONCERN)(CARE)

• He's terribly concerned about you(Está muy preocupado por ti)
• Your family doesn't care about you(Tu familia ni se preocupa por ti)

por = for (Duration)(How long it takes)

• It'll just be for a little while(Será por poco tiempo)

por = by, on, for, through (means of communication)(way of communication)

• Please contact us by telephone or by email(Póngase en contacto con nosotros por teléfono)
• I'm the "company" you phoned for(Soy la "compañía" que pediste por teléfono..)
• Agree to talk on the phone(Estuvo de acuerdo en hablar por teléfono)
• I traveled through Italy(viajé por Italia)

por = to, to be, still or yet to be, not yet (something that has not been resolved)

• We have a lot of work to do(Tengo mucho trabajo por hacer)
• The letter is still to be or remains to be written (la carta está por escribirse)

por = for (exchanges)

• Te lo cambio por tu hamburguesa(I'll trade you for your burger)

por=as, for, as being (IN MISCELLANEOUS USES)

• To take as one's wife (tomar por esposa)
• I had my father as of for my teacher(Tuve a mi padre por maestro)

por=by (used in oaths)

• by God(por Dios)

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para = (purpose)(goals)(why something is done)

• If you want to win, you got to suffer!(Para ganar, tienen que sufrir!)

para = for (recipients)

• Salgo para Colombia mañana(I leave for Colombia tomorrow)
• This is for you(esto es para ti)

para = by, for (deadlines)

• I need it for tomorrow(Lo necesito para mañana)
• I need this by Wednesday(Lo necesito para el miércoles)

para = (SEGUIDO DE UN INFINITIVO)/para hacer algo = to do something

• I'm ready to start(estoy listo para empezar)

These are just some of the examples of possible applications.