minor key vs minor mode

minor key and minor mode both are nouns.

Word	Noun	Adjective	Verb	Adverb
minor key	Yes	No	No	No
minor mode	Yes	No	No	No

As nouns, minor key and minor mode are synonyms defined as:

minor key (noun)	minor mode (noun)
a key based on the minor scale	a key based on the minor scale