OK, this is off the top of my head, but here goes. 

In Joseph, the narrator is the only lead with the brothers as the featured roles.  The others that sing are mostly supporting since they generally appear in only one scene.

Nathan, Adelade, Sarah and Sky are the leads with the other singing soloists as supporting except for Nicely-Nicely (thank you) who is featured.  Nicely is not a lead since no part of the plot involves him. Big Julie is a small featured role unless you get huge applause in which case my own ego would make me think I'm Featured.

Typically I think of the soloist in a musical as featured (except for leads) unless one or two characters are what I consider "second bananas", the comedians. They are also featured. 

I guess the featured roles are the non-leads with many scenes or multiply songs. 

Remember.....there are no small roles....merely small minded directors who don't give me the lead.

You might be closer with your order and probably supporting and featured are one and the same. 

As for Joseph. I've only seen the show twice but my memory is the narrator singing more then Joe.  If this is true then I would say Joseph is a second lead or main principle.

I told you this was off the top of my head

Originally posted by TheActingTechie and the narrator simply helps transition from scene to scene.? She never has a song that she performs alone, but is in every virtually every number.? ensemble.

Doesn't she sing Prolouge and Pharoh Story by herself?

This question comes up occasionally, and I always wonder:  why do you care?  If we call Big Jule a principal, does that make it a better role?

Equity's LORT contract says anything that isn't chorus is a principal.

The Tony rules essentially say a leading role is whatever they say it is.

I say:  If it's on my resume, it's a lead.  If it's on your resume, it's featured.  If it's on somebody else's resume, it's supporting. 

POB  LOL