I've been trying to find a simple definition online for a while now with no luck so I thought I'd ask here. What is the difference in finding the argument of a complex number and the principle argument of a complex number.

For example given 8 + 8 sqrt(3)i I know that the argument is pi/3 and the modulus is 16, but I'm unsure about how what I need to do to find the principle argument.

Can anyone give me some help?