common mood vs mood

common mood and mood both are nouns.

Word	Noun	Adjective	Verb	Adverb
common mood	Yes	No	No	No
mood	Yes	No	No	No

As nouns, mood is a hypernym of common mood; that is, mood is a word with a broader meaning than common mood:

common mood: a mood (grammatically unmarked) that represents the act or state as an objective fact
mood: verb inflections that express how the action or state is conceived by the speaker

Other hypernyms of common mood include modality, mode.

common mood (noun)	mood (noun)
a mood (grammatically unmarked) that represents the act or state as an objective fact	a characteristic (habitual or relatively temporary) state of feeling
	verb inflections that express how the action or state is conceived by the speaker
	the prevailing psychological state