This might be a stupid question, but I haven't found an answer.
When is a key of a song minor? Because, I know the major keys and the formula:
I, ii, iii, IV, V, vi, vi
If a key is minor, so it means it comes from a minor scale?

Is there a way to "reach" it from the major scale, because I read you only need to know that the major scale.
Thanks!