opac·​i·​ty | \ ō-ˈpa-sə-tē How to pronounce opacity (audio) \
plural opacities

Definition of opacity

1a : obscurity of sense : unintelligibility
b : the quality or state of being mentally obtuse : dullness
2 : the quality or state of a body that makes it impervious to the rays of light broadly : the relative capacity of matter to obstruct the transmission of radiant energy
3 : an opaque spot in a normally transparent structure (such as the lens of the eye)

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Examples of opacity in a Sentence

the opacity of the glass Critics have noted the opacity of her writing style.

Recent Examples on the Web

Apple’s infamous opacity around new products means the app makers don’t have many answers yet as to how Apple’s sign in mechanism is going to impact their apps. Lauren Goode, WIRED, "App Makers Are Mixed on ‘Sign In With Apple’," 15 June 2019 In times like these, the company’s opacity has taken on an extra cost. Dan Gallagher, WSJ, "Google’s Search Business Needs More Answers," 1 May 2019 But even if the RealImpact system works, its opacity is a real concern which places the potentially valuable details of this public good solely in the hands of a private for-profit company. David Grossman, Popular Mechanics, "AccuWeather Unveils Its Own Hurricane Scale," 14 Jan. 2019 The film is actually about two brinks, one of them clearly defined and the other not, though no less significant for its opacity. Joe Morgenstern, WSJ, "‘The Brink’ Review: In the Mind of a Propagandist," 28 Mar. 2019 The researchers' model predicts that these waves, which mainly depend on the opacity of iron, will lead to temperature fluctuations on the order of a week as well. Chris Lee, Ars Technica, "Beautiful 3D model of stars explains changes in brightness," 8 Oct. 2018 Once faddish, New Historicism has faded, as all trends of literary criticism do, a victim of its own interpretive distortions and linguistic opacity. Charles Mcnulty, latimes.com, "In 'Tyrant,' Harvard professor Stephen Greenblatt turns to Shakespeare for answers to Trump," 22 May 2018 Once the sky’s opacity reaches a low enough level, the agency will decide whether to begin the 45-day listening period. John Wenz, Popular Mechanics, "Opportunity May Not Come Back Until January. NASA May Not Give It That Long.," 1 Sep. 2018 Central bankers a generation ago prided themselves on silence and opacity. Nick Timiraos, WSJ, "Fed Weighs Wait-and-See Approach on Future Rate Increases," 6 Dec. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'opacity.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of opacity

1575, in the meaning defined at sense 1a

History and Etymology for opacity

Middle French opacité shadiness, from Latin opacitat-, opacitas, from opacus shaded, dark

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Statistics for opacity

Last Updated

22 Jun 2019

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Time Traveler for opacity

The first known use of opacity was in 1575

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More Definitions for opacity



English Language Learners Definition of opacity

: the quality of a material that does not allow light to pass through it : the quality of being opaque
formal : the quality of being difficult to understand or explain


opac·​i·​ty | \ ō-ˈpas-ət-ē How to pronounce opacity (audio) \
plural opacities

Medical Definition of opacity

1 : the quality or state of a body that makes it impervious to the rays of light broadly : the relative capacity of matter to obstruct by absorption or reflection the transmission of radiant energy (as X-rays, infrared radiation, or sound)
2 : an opaque spot in a normally transparent structure (as the lens of the eye)

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