"sino" vs "pero"
both means "but ...". What is the difference?
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.
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