Why are these two sentences different? One uses "para comprar" and the other just "comprar." I want to understand the rule that allows you to omit "para" before an infinitive.
1. Le costó 5 dólares comprarlo de nuevo.
2. Él necesita 5 dólares para comprarlo.
Hola Richard
The functions of "comprarlo" are different in each sentence.
1. Le costó 5 dólares comparlo de nuevo.
Here "comprarlo de nuevo" is the subject of the sentence. You can see it better if you change the order: Comprarlo de nuevo le costó 5 dólares. (Buying it again cost him 5 dollars). It's a bit difficult to see as it is an infinitive, but you can see how we use the infinitive as subjects here.
You can also find this specific use of "costar" in this lesson where you'll see some similar examples.
2. Él necesita 5 dólares para comprarlo.
Here "para comprarlo" is a clause introduced by "para" which expresses a purpose. You do need para with this meaning. Here is a lesson on this use of para.
I hope this helps.
Saludos cordiales
Inma
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