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

His other healthcare venture, Cost Plus Drugs, has similarly sought to reduce opacity in pharmaceutical pricing. —Catherina Gioino, Fortune, 26 Mar. 2026

Sovereign asset owners are seeking market rails that compress settlement latency, reduce operational opacity, and support enforceable governance across jurisdictions. —Wyles Daniel, USA Today, 23 Mar. 2026

What to read next Plus, our SMS atmosphere models still need to include things like molecular opacities and models for stars cooler than 7,000 Kelvin, which could clear up some of these discrepancies. —Paul Sutter, Space.com, 23 Mar. 2026

Thousands of relatives of Iranian officials were believed to be living across Western countries, IranWire reported in 2022, though precise figures remain difficult to independently verify, underscoring both the scale of the phenomenon and the opacity of the system behind it. —Efrat Lachter, FOXNews.com, 21 Mar. 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
• loquacity
• mendacity
• pugnacity
• 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)