When is 'sino" to be used
I would like to know when the preposition "sino" is to be used and how it is used.
3 Answers
"Sino" should be used when you are setting something up against something else such as: "No lo hizo él, sino ella." "He didn't do it, she did". or "No solo es listo, sino también trabajador." "He's not only clever but also hardworking."
"Sino" can also be used as "except" "¿Quien sino tú lo haría?" "Who else but you would do it?" "No quiero sino que se haga justicia." "I only want justice to be done."
I hope this helps you a little bit. Just a side note, even though I knew what the word meant, I just picked up a couple of more words for my lexicon in spanish!! Thanks for the post. 
Lesson 3.15 covers that - worth watching the video.
As far as I remember it translates as 'rather' - 'but' used after a negative;
E.g He does not run, rather he walks
No corre, sino anda
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