Just Bought A 12 String

[ProfessorGAC]

12. Fair Question

I was taught that the 9th was added after a dominant 7, and if the seventh if not present is a sus9. Or a Maj9.
Like adding an F# to an A7, where the 7th is internal (on piano). So, G, A, C#, E, F#. Since the dom7 is there, we call it a 13. Leave out the G, it's A6. That's how I was taught anyway.
But, calling it a Sus2 would mean the same darned thing. So, we probably can do whichever we like best.