opacity

noun

Etymology: From opaque + -ity, from French opacité, from Latin opacitas.

1. The state or quality of being opaque, not allowing light to pass through.

   “We could not see the sandbar due to the opacity of the muddy water.”

2. The state or quality of being inaccessible to understanding.

   “The opacity of these decisions is troubling.”

3. A measure of relative impenetrability to electromagnetic radiation such as light.

   “The opacity of a clean glass window is near zero.”

4. An opaque area.

   “This report concerns a child with Down's syndrome (mongolism) and bilateral congenital corneal opacities born into a family affected through three generations by Rieger's anomaly.”

   “Scanty irregular opacities are not uncommonly observed on the chest roentgenogram in the absence of interstitial fibrosis of the lungs.”