Open strings on guitar in standard tuning is actually an A 11 chord. EADGBE, A+E are related by fifths implying A as the root with the fifth (E) in the bass, the G is a minor 7th than the B+D are a 9th and an 11th stacked on top of the 7th. You could also call it an A7add11 .
A E half dimished chords would be EGBbD and fully dimished is EGBbDb.
I play guitar, Bass guitar and Double bass, piano (poorly), saxaphone (just learning to play), Computer (sequencers, reason, protools, logic, etc), Some drums, some singing,