"sino" vs "pero"
both means "but ...". What is the difference?
they both mean "but". You use 'pero' when the second part of the sentence add information to the first one- "he loves to record girls, but secretly". You use 'sino' when the second part of the sentence is used to correct the first part- "they didn't tell the police, but their families". With 'sino' the first part is always negative, and the second one is its correction. Hope that answers it :D
Sino is an elegant way to provide a non-obvious alternative to a negative statement, without having to start a new sentence.
To avoid confusing it with pero, try replacing it with although–if it works, it's pero; otherwise, it's sino.
> — Me apetecía verte hoy, pero hasta mañana no puedo.
> "I felt like seeing you today, (but/although) until tomorrow, I can't."
> — Pues yo no contaba con verte hoy, sino mañana, así que perfecto.
> "(Well) I wasn't counting on seeing you today, (but/I was counting on seeing you) tomorrow, so that's perfect."
I go deep into the usage context of sino in this NachoTime post.