Actually, the mistake that non-native Spanish speakers make is using “pero” in a sentence when they should be using “sino” and vice versa.

How To Use The Words Pero vs. Sino In Spanish

By the way, both “pero” and “sino” mean the English word “but.” But “pero” is more like the English words “nevertheless” and “yet.” On the contrary, “sino” is similar to the English word “rather” or “on the contrary.”

Here’s an example of the CORRECT use of “pero”

Dormir puede ser bueno para la salud, pero yo prefiero salir.

(Sleeping can be good for your health, but I prefer to sleep.)

I have an American friend who is studying Spanish at one of the major universities here in Medellín. Saturday night he telephoned me and said:

“Patrick, no quiero estudiar esta noche, PERO rumbiar en una discoteca.”

(*** Note that the “Paisas” or people of Medellín pronounce the word “rumbiar” instead of “rumbear” — It’s a Paisa thing!)

His use of the word “pero” was ABSOLUTELY INCORRECT. My first reaction was to correct his Spanish grammar and tell him, NO, you have to say:

“no quiero estudiar esta noche, sino rumbiar en una discoteca.”

“I don’t want to study tonight, but (on the contrary, I want to) go party in a club.”

I didn’t bother to correct his Spanish grammar because he’s the type of guy who would have impolitely told me “Patrick, how would you know? You’re not from Colombia. You’re from New York.”

Although he would have meant to say . . .

“Patrick no eres colombiano SINO nuyorquino.”

Patrick you are not a Colombian but (on the contrary you are) a New Yorker.

So “me quedé callado” (I kept quiet) but made a note to warn my readers of this pitfall so that you don’t make the same mistake that “mi amigo gringo” (my American friend) made.

Here are some more examples with the CORRECT usage of the word SINO.

Este carro no ES doméstico sino importado.
This car isn’t domestic but (on the contrary) imported.

El hombre no ERA haitiano sino jamaiquino.
The man wasn’t Haitian rather Jamaican.

And here are some examples with the correct use of PERO.

El pajarito se cayó del nido, pero no se lastimó.
The bird fell from the nest, but (nevertheless) it didn’t hurt itself.

Este restaurante es muy caro, pero la comida sabe deliciosa.
This restaurant is very expensive, but (nevertheless) the food is delicious.”

So how do you know when to use “pero” and when do you use “sino”?

If you read the Spanish grammar books on the market you will come across rules that just aren’t correct — or rules that just don’t work in real life. For example, in one my “favorite” Spanish grammar books, it says “if there is a negative clause in the first part of the sentence, then PERO changes to SINO.” And that’s not correct. I can give you tons of examples where you would use PERO even though the first clause of the sentence is negative. Por ejempo:

Mi papá no era rico, pero era feliz.
My dad wasn’t rich but he was happy.

No es cocinera, pero le gusta cocinar.
She isn’t a chef but she likes to cook.

So what do I do so that I ALWAYS know when to use “pero” and when to you use “sino”?

You will want to pay attention to what I call my “regla casera” (home-made rule) because you are not going to find this rule in any Spanish grammar book.
But it works.

Here’s my simple rule . . .

I ask myself do I want to show a DIRECT CONTRAST between the second clause and the first clause of a
sentence. If the answer is “no,” then I use “pero” And if the answer is “yes” then I use “sino.”

In my above examples where I used SINO, I was trying to show a DIRECT CONTRAST.

Este carro no ES doméstico sino importado..

I was trying to show a DIRECT CONTRAST between the car being imported, and indicate that it is domestic.

El hombre no ERA haitiano sino jamaiquino.

I was trying to show a DIRECT CONTRAST between the man being Jamaican and indicate that he is Haitian.

And in the sentences where I used PERO I was NOT trying to show a DIRECT CONTRAST:

El pajarito se cayó del nido, pero no se lastimó.

Here, I am not trying to directly contrast or contradict that the bird fell from the nest, I was just adding that the bird was not hurt.

Este restaurante es muy caro, pero la comida sabe deliciosa.

Here, I am not trying to directly contrast or contradict that the restaurant is expensive, I was just adding that the food is delicious.