Originally posted by concrete chaos
is there a specific way in which you decide whether its maj or min....

Yes dude , it's the root chord ... In the C ionian , the root chord is Cmaj that's why it's a major mode , as for the D dorian, the root chord is Dmin so Dorians are minor modes, and so with the rest of the modes.

The exception is the locrian mode , since the root is a diminished chord ... I don't remember what do they call it, diminished mode I think.