opaqueness

Concise Oxford English Dictionary © 2008 Oxford University Press:
opaque /ə(ʊ)ˈpeɪk/

▶adjective (opaquer, opaquest)

• 1 not able to be seen through; not transparent.

• 2 difficult or impossible to understand.

▶noun an opaque thing.

■ Photography a substance for producing opaque areas on negatives.

– derivatives
opaquely adverb,
opaqueness noun.

– origin ME opake, from L. opacus ‘darkened’.