focal

focal
    adj 1: having or localized centrally at a focus; "focal point";
           "focal infection"
    2: of or relating to a focus; "focal length"
    

Focal \Fo"cal\, a. [Cf. F. focal. See {Focus}.]
   Belonging to,or concerning, a focus; as, a focal point.
   [1913 Webster]

   {Focal distance, or length, of a lens or mirror} (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. 

   {Focal distance of a telescope}, the distance of the image of
      an object from the object glass.
      [1913 Webster]
    

FOCAL

   1. FOrmula CALculator.

   An interactive system written by Rick Merrill of {DEC} in 1969
   for {PDP-5} and {PDP-8}.  It was a descendant of {AID}/{JOSS}.

   Versions: FOCAL-69, FOCAL-1971, FOCAL-11 (for {PDP-11} under
   {RT-11}).

   (1994-12-21)

   2. Forty-One CAlculator Language.

   The programming language of the HP-41 calculator line.

   (1994-12-21)
    

66 Moby Thesaurus words for "focal":
      approaching, arch, asymptotic, banner, basic, bedrock, capital,
      cardinal, central, centralized, centred, centripetal, centrolineal,
      champion, chief, concentrated, concurrent, confluent, confocal,
      connivent, convergent, converging, crowning, dominant, essential,
      first, foremost, fundamental, great, headmost, hegemonic,
      indispensable, leading, life-and-death, life-or-death, magisterial,
      main, master, material, meeting, mutually approaching,
      of vital importance, overruling, paramount, predominant,
      preeminent, preponderant, prevailing, primal, primary, prime,
      principal, radial, radiating, ranking, ruling, sovereign, star,
      stellar, substantive, supereminent, tangent, tangential, topflight,
      uniting, vital