noun, plural o·pac·i·ties.
  1. the state or quality of being opaque.
  2. something opaque.
  3. the degree to which a substance is opaque; capacity for being opaque.
  4. Photography. the proportion of the light that is absorbed by the emulsion on any given area of a film or plate.
  5. obscurity of meaning.
  6. mental dullness.
  7. Medicine/Medical. an opaque spot or area in normally clear or transparent tissue, as a cataract of the eye.

Origin of opacity

First recorded in 1550–60, opacity is from the Latin word opācitās shade. See opaque, -ity
Related formsnon·o·pac·i·ty, noun, plural non·o·pac·i·ties.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for opacities

murkiness, obscurity, darkness

Examples from the Web for opacities

Historical Examples of opacities

British Dictionary definitions for opacities


noun plural -ties
  1. the state or quality of being opaque
  2. the degree to which something is opaque
  3. an opaque object or substance
  4. obscurity of meaning; unintelligibility
  5. physics photog the ratio of the intensity of light incident on a medium, such as a photographic film, to that transmitted through the medium
  6. logic philosophy the property of being an opaque context
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for opacities



1550s, "darkness of meaning, obscurity," from French opacité, from Latin opacitatem (nominative opacitas) "shade, shadiness," from opacus "shaded, dark, opaque" (see opaque). The literal sense "condition of being impervious to light" first recorded 1630s.

Online Etymology Dictionary, © 2010 Douglas Harper

opacities in Medicine


  1. The quality or state of being opaque.
  2. An opaque or nontransparent area, as of the cornea.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.