achromatic

Concise Oxford English Dictionary © 2008 Oxford University Press:
achromatic /ˌakrə(ʊ)ˈmatɪk/

▶adjective

• 1 relating to or denoting lenses that transmit light without separating it into constituent colours.

• 2 without colour.

– derivatives
achromaticity noun,
achromatism noun.

– origin C18: via Fr. from Gk a- ‘without’ + khrōmatikos (from khrōma ‘colour’).