vagueness vs fogginess

vagueness and fogginess both are nouns.

Word	Noun	Adjective	Verb	Adverb
vagueness	Yes	No	No	No
fogginess	Yes	No	No	No

As nouns, fogginess is a hypernym of vagueness; that is, fogginess is a word with a broader meaning than vagueness:

Other hypernyms of vagueness include blurriness, fuzziness, indistinctness, softness.

vagueness (noun)	fogginess (noun)
unclearness by virtue of being poorly expressed or not coherent in meaning	the quality of being indistinct and without sharp outlines
indistinctness of shape or character	an atmosphere in which visibility is reduced because of a cloud of some substance