opacity

American  

[oh-pas-i-tee] / oʊˈpæs ɪ ti /

noun

plural

opacities

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

• nonopacity noun

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

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 distinction is deliberate: Option A trades scrutiny for relief; Option B trades opacity for exposure.

From The Wall Street Journal • Mar. 20, 2026

He was instantly struck by the opacity of an investment bank’s books.

From "The Big Short" by Michael Lewis