Coxeter point group rank is equal to the number of nodes which is also equal to the dimension. A single mirror exists in 1-dimension, [ ], , while in 2-dimensions [1], or [ ]×[ ]. The 1 is a place-holder, not an actual branch order, but a marker for an orthogonal inactive mirror. The notation [ n,1], represents a rank 3 group, as [ n ]×[ ] or . Similarly, [1,1] as [ ]×[ ] ×[ ] or order 2 and [1,1] as [ ] ×[ ] ×[ ] or , order 1!