Opacity
How much a material blocks light from passing through — fully opaque means no light gets through at all.
Technical definition
Opacity is the inverse of transparency; a fully opaque surface transmits none of the incident light, reflecting or absorbing all of it instead.
Common confusion
Opacity (light transmission) is a different property from finish (matt/gloss, which is about surface reflection), though both affect how a colour reads.
Example
A solid emulsion wall paint is opaque; a coloured glass pane is not.
Why it matters
Paint opacity/coverage affects how many coats are needed and how much an existing wall colour shows through.
Related terms
Sources
- Colourwise editorial synthesis — Colourwise