Definition:Harmonic Wave/Wave Number

Definition
Let $\phi$ be a harmonic wave expressed as:
 * $\forall x, t \in \R: \map \phi {x, t} = a \map \cos {\omega \paren {x - c t} }$

The wave number $k$ of $\phi$ is the number of wavelengths of $\phi$ per unit distance along the $x$-axis.

Also known as
The term wave number can also be seen as wavenumber.

Also see

 * Wave Number of Harmonic Wave: this wave number is shown to be $\dfrac 1 \lambda$, where $\lambda$ is the wavelength of $\phi$