rydberg unit vs wave number

rydberg unit and wave number both are nouns.

Word	Noun	Adjective	Verb	Adverb
rydberg unit	Yes	No	No	No
wave number	Yes	No	No	No

As nouns, wave number is a hypernym of rydberg unit; that is, wave number is a word with a broader meaning than rydberg unit:

rydberg unit: a wave number characteristic of the wave spectrum of each element
wave number: the reciprocal of the wavelength of a wave

rydberg unit (noun)	wave number (noun)
a wave number characteristic of the wave spectrum of each element	the reciprocal of the wavelength of a wave