Pero vs. Sino

Both pero and sino are used as conjunctions to link contrasting ideas, like the English, 'but'. The difference is that sino corrects or negates the information that has come before it, while pero does not. Sino is only used in negative sentences, while pero is in affirmative sentences

Pero: But

Me gustaría salir, pero no puedo

Marcela es linda pero no es intelegente

Hace frío, pero también hace sol

I would like to go out, but I can't

Marcela is pretty, but not intellegent

It's cold, but also sunny


Sino: But, Rather

Alfredo no es alto sino bajo

No es tonto, sino demasiado inteligente

No voy a estudiar matemática, sino arte

Alfredo isn't tall, but (rather) short

He is not stupid, but (rather) too intelligent

I'm not going to study math, but (rather) art