An Etymological Dictionary of Astronomy and Astrophysics

Describing a lens or optical system with a convergent power of zero, whose object and image points stretch to infinity. Thus,
→ afocal system.

Etymology (EN): Afocal, from → a- + → focal.

Etymology (PE): Akânun, from a- negation prefix, → a- + kânun, → focus. Bikânun, from bi- negation prefix + kânun, → focus.