Help with sets

[Lawrence D'Oliveiro]

In message
<aa6eafa0-7075-424c-abef-79cbc0dd3359 at w19g2000yqb.googlegroups.com>, Steve 
Howell wrote:

> I guess a lot depends on how you define "symmetry."  Is your
> definition of "symmetry" equivalent to your definition of
> "orthogonality"?

No idea. It’s just that the example being discussed in this thread seemed to 
come under the old term “orthogonality”, so I wondered why a different term 
was being used.

So far no-one has come up with a good excuse for using a different term.