from The American Heritage® Dictionary of the English Language, 5th Edition.

  • adjective Of or relating to a focus.
  • adjective Placed at or measured from a focus.

from The Century Dictionary.

  • Of or pertaining to a focus: as, a focal point.
  • In optics, of a mirror or lens, the distance (also called the focal length) from its center to the principal focus (see focus); of a telescope, the distance between the focal plane and the object-glass.

from the GNU version of the Collaborative International Dictionary of English.

  • adjective Belonging to,or concerning, a focus; as, a focal point.
  • adjective (Opt.) the distance of the focus from the surface of the lens or mirror, or more exactly, in the case of a lens, from its optical center.
  • adjective the distance of the image of an object from the object glass.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • adjective Belonging to, concerning, or located at a focus
  • adjective medicine limited to a small area

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adjective of or relating to a focus
  • adjective having or localized centrally at a focus


from Wiktionary, Creative Commons Attribution/Share-Alike License

From New Latin focālis; synchronically analyzable as focus +‎ -al.



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