millivolt vs potential unit

millivolt and potential unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
millivolt	Yes	No	No	No
potential unit	Yes	No	No	No

As nouns, potential unit is a hypernym of millivolt; that is, potential unit is a word with a broader meaning than millivolt:

millivolt: a unit of potential equal to one thousandth of a volt
potential unit: a measure of the potential energy of a unit charge at a given point in a circuit relative to a reference point (ground)

millivolt (noun)	potential unit (noun)
a unit of potential equal to one thousandth of a volt	a measure of the potential energy of a unit charge at a given point in a circuit relative to a reference point (ground)