## Orthogonality

There are several definitions of *orthogonality*:

- Two Euclidean vectors are
*orthogonal* if they are perpendicular, i.e., they form a right angle.
- Two vectors, $\mathbf x$ and $\mathbf y$ are
*orthogonal* if their Inner Product $\mathbf x^T \mathbf y = 0$ This relationship is denoted $\mathbf x \, \bot \, \mathbf y$: Vector Orthogonality
- Two Vector Subspaces are
*orthogonal* if each vector from one subspace is orthogonal to each vector of another subspace: Space Orthogonality
- Two Functions are orthogonal if their inner product is 0: Orthogonal Functions

## Sources