opacity

noun

1.
the phenomenon of not permitting the passage of electromagnetic radiation
Antonym:
transparency
Derived from:
opaque
2.
incomprehensibility resulting from obscurity of meaning
opaqueness
Derived from:
opaque
3.
the quality of being opaque to a degree; the degree to which something reduces the passage of light
opaqueness
Antonym:
clarity
Derived from:
opaque