\begin{definition}[Definition:Orthogonal (Linear Algebra)/Sets]
Let $\struct {V, \innerprod \cdot \cdot}$ be an inner product space.
Let $A, B \subseteq V$.
We say that $A$ and $B$ are '''orthogonal''' {{iff}}:
:$\forall a \in A, b \in B: a \perp b$
That is, if $a$ and $b$ are orthogonal elements of $A$ and $B$ for all $a \in A$ and $b \in B$.
We write: 
:$A \perp B$
\end{definition}