opacity vs muddiness

opacity and muddiness both are nouns.

Word	Noun	Adjective	Verb	Adverb
opacity	Yes	No	No	No
muddiness	Yes	No	No	No

As nouns, muddiness is a hyponym of opacity; that is, muddiness is a word with a more specific, narrower meaning than opacity:

opacity: the quality of being opaque to a degree; the degree to which something reduces the passage of light
muddiness: the quality of being cloudy

Other hyponyms of opacity include cloudiness, murkiness, blurriness, fogginess, fuzziness, indistinctness, softness.

opacity (noun)	muddiness (noun)
the quality of being opaque to a degree; the degree to which something reduces the passage of light	the quality of being cloudy
incomprehensibility resulting from obscurity of meaning	a mental state characterized by a lack of clear and orderly thought and behavior
the phenomenon of not permitting the passage of electromagnetic radiation	the wetness of ground that is covered or soaked with water