opacity

American  

[oh-pas-i-tee] / oʊˈpæs ɪ ti /

noun

opacities plural

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.

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opacity British  

/ əʊˈpæsɪtɪ /

noun

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

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Other Word Forms

Derived Forms

• nonopacity
  noun

Inflected Forms

Nouns

• opacities
  plural

Etymology

Origin of opacity

First recorded in 1550–60, opacity is from the Latin word opācitās shade. See opaque, -ity

Explanation

Opacity is the characteristic of being difficult to understand or unclear. A professor whose lectures are known for opacity is going to find himself in a room full of some very frustrated students. In its literal sense opacity is used to talk about objects that don't allow light to shine through. A window that has accumulated a lot of dirt and dust is characterized by its opacity, as opposed to a transparent window, which is one you can see right through. The word opacity is used more generally for anything obscure, unclear, or incomprehensible, like the opacity of a novel full of ten-syllable words or a dictionary that doesn't give you any clear or straightforward definitions.

Example Sentences

See Examples For:

opacity opacities

While there is no evidence such interference played a role in the changes, the opacity regarding them has raised some eyebrows.

From The Wall Street Journal ● Jul. 19, 2026

The experience of the nonagency mortgage-backed securities market before the 2008 financial crisis shows how opacity can enable misrepresentations of asset quality, erode investor confidence and contribute to market unraveling.

From MarketWatch ● Apr. 13, 2026

With the stakes as high as they are, the president's opacity is notable.

From BBC ● Apr. 6, 2026

In this context, opacity feels comfortable and commonplace.

From Slate ● Apr. 4, 2026

The opacity of his classroom manner reflected his own insecurity with newly discovered phenomena that require a novel cast of mind to understand even today.

From "Big Science" by Michael Hiltzik

Ground-glass opacities — a sign that’s common in COVID-19 patients — showed up on his scans.

From Los Angeles Times ● Mar. 31, 2025

When Sovannarie was 3 months old, her parents noticed something unusual about their daughter: white opacities in both pupils.

From Salon ● Dec. 11, 2022

The panels come in different opacities — some are clear, while others block more UV light for sun protection.

From Seattle Times ● Mar. 25, 2021

She ordered a scan of my lungs to see if ground-glass opacities, or light-colored patches, appeared, a sign that Covid had affected my lungs.

From New York Times ● Jan. 21, 2021

How far more subtle the appeal of these grey and dun-coloured opacities, these tent-cloths of fog pressed out into uncouth, dumbly pathetic shapes by the struggle for existence that seethes below it always—always!

From Wandering Heath by Quiller-Couch, Arthur Thomas, Sir