digit vs linear unit

digit and linear unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
digit	Yes	No	No	No
linear unit	Yes	No	No	No

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

Other hypernyms of digit include linear measure.

digit (noun)	linear unit (noun)
a finger or toe in human beings or corresponding body part in other vertebrates	a unit of measurement of length
one of the elements that collectively form a system of numeration
the length of breadth of a finger used as a linear measure