Linear Algebra/Orthogonal Sets
Orthogonal Sets 
Given a set , where through are nonzero vectors of the same dimension, is an orthogonal set if
So, for example, if one has a set of 3 vectors with the same dimension (for example ) and taking the dot product of each vector with each other vector all equal zero, it is an orthogonal set. This is illustrated below.
Example of Orthogonal Set 
We see that
Thus, is an orthogonal set of vectors.