opacity

noun

opac·​i·​ty ō-ˈpa-sə-tē 

plural opacities

1

a

: 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)

Synonyms of opacity

• ambiguity
• ambiguousness
• mysteriousness
• opaqueness

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

One such product is Biodance’s Bio-Collagen mask, which applies like your average milky white sheet mask but turns clear after a few hours; the opacity change signifies that the ingredients have been absorbed by the skin. — Kiana Murden, Vogue, 25 Sep. 2026

The report found that the 340B program uses billions in financial benefits with troubling opacity. — Christina Smith, Baltimore Sun, 24 Sep. 2026

There’s an opacity around how the models are tested collectively and what the White House standards are for releasing. — Fortune Editors, Fortune, 15 Sep. 2026

Aside from this feature, iOS 27 also includes a way to adjust the opacity of Liquid Glass, new icon designs, extra-large widgets, and new volume settings for ringtones, alarms, timers, and alerts. — Emma Roth, The Verge, 9 Sep. 2026

Word History

Etymology

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

First Known Use

1575, in the meaning defined at sense 1a

Rhymes for opacity

• audacity
• capacity
• fugacity
• loquacity
• mendacity
• rapacity
• sagacity
• tenacity
• veracity
• vivacity
• voracity
• incapacity

Kids Definition

opacity

noun

opac·​i·​ty ō-ˈpas-ət-ē 

plural opacities

: the quality or state of being opaque

Medical Definition

opacity

noun

opac·​i·​ty ō-ˈpas-ət-ē 

plural opacities

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)