footer vs linear unit

footer and linear unit both are nouns.

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

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

footer: (used only in combinations) the height or length of something in feet
linear unit: a unit of measurement of length

Other hypernyms of footer include linear measure.

footer (noun)	linear unit (noun)
a printed note placed below the text on a printed page	a unit of measurement of length
a person who travels by foot
(used only in combinations) the height or length of something in feet