Designating or relating to two or more lenses (especially in a microscope) the focal points of which lie in the same plane, so that they may be interchanged without the need to adjust the focus.
Origin
Late 19th century. From par + focal.
Definition of parfocal in US English:
parfocal
adjectivepɑːˈfəʊkl
Optics
Designating or relating to two or more lenses (especially in a microscope) the focal points of which lie in the same plane, so that they may be interchanged without the need to adjust the focus.