Why pero and not sino?

Hi Becky,

Sino wouldn't work in that particular sentence though I can see why you think it should. You would need a very different sentence, as it is designed specifically to make the use of pero clear.

In the lesson there is a clarification which made all the difference for me. They give two sentences and I have copied / pasted the paragraph. 

""Money is not everything but it helps a lot" and "Andrea is not a boys name but a girl's name." In the first example we are adding an idea that makes a contrast with the first negative idea (pero). In the second example we are not adding an idea but giving a substitute to the first negative idea (sino)." 

So in your sentence "No puedo salir hoy pero saldré mañana" the meaning is like "I can't go out today BUT I CAN go out tomorrow." She/He is offering / adding another possibility or idea; she /he wants to go out but can't do so today. It's a subtle difference but when you look at the "sino" examples it begins to make sense.

I hope that helps.

John

I think “No puedo salir hoy sino mañana” could be correct.  Imagine that Becky’s friend comes over to her at school and says, “I hear that you can go out tonight.”  She responds, “I can’t go out tonight but tomorrow I can”.  That would work with “sino”.  But in the quiz question it’s easier:  the verb is changed, so we can’t use “sino”.