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An italic k or a tilde-topped nu, waves per unit length.
Also known as: Wave number, Spatial frequency, Reciprocal wavelength, Nu tilde
Wavenumber counts how many waves fit into a unit of length, and it comes in two incompatible flavours: spectroscopists use ν̃ = 1/λ in reciprocal centimetres, physicists use k = 2π/λ. The two differ by 2π and by a factor of a hundred, and both are called the wavenumber.
Denotes the number of waves per unit length, the reciprocal of the wavelength.
Contexts: Laboratory
Has two current definitions differing by 2π: the spectroscopic ν̃ = 1/λ and the angular k = 2π/λ, both routinely called 'wavenumber'.
Contexts: Laboratory
Is reported in reciprocal centimetres in infrared spectroscopy, a non-SI unit retained because the numbers are convenient.
Contexts: Laboratory
An italic lowercase letter k, or a Greek nu carrying a small wavy stroke above it.