When to add prepositions before an infinitive verb (por/para/a/de)?

Question

With the infinitive form of a verb in English, (e.g. to speak), the word 'to' seems to convey a specific meaning where, in Spanish, an additional preposition is used in some cases.Examples:>I can use running shoes to run fasterThe direct English translation is:>Puedo usar zapatillas correr más rápido Seemingly, the more correct Spanish expression is:>Puedo usar zapatillas para correr más rápidoIf we take the correct expression to include the preposition 'para' , which signals a reason or means 'in order to', in the English, the word 'to' here covers that meaning as well as forms the infinitive. I was wondering if there are some common rules for when to place prepositions before infinitive verbs, and which to use. (Such as ir+a+infinitive).

Answer 1

Great question! Generally speaking, an infinitive will most likely be preceeded by either a conjugated verb or a preposition. Which type of preposition necessary depends on the context. Are you using a phrase that already requires a certain preposition? Or are you talking about that "in order to" which then requires para? It all boils down to communication and understanding what the speaker/writer is truly expressing.

Here are some examples for you:

1. Conjugated verb before infinitive (no preposition required): Quiero comer una manzana. I want to eat an apple.
2. ACABAR + de: Acabo de volver de Chile. I just got back from Chile.
3. IR + a: ¡Vamos a bailar! We're going dancing/Let's dance!
4. ESTAR + por - "about to [do X]": Estaba por salir cuando me llamó Juan. I was about to leave when Juan called me.
5. Antes de/Después de Antes de irse, Marta apagó las luces. Before leaving, Marta turned off the lights. - Después de terminar el examen, los estudiantes se compraron helados. After finishing the exam, the students bought themselves ice cream.

There are, of course, more possibilities. I hope this helps, though!