alpha and omega

from WordNet (r) 3.0 (2006)

alpha and omega
    n 1: the first and last; signifies God's eternity
    2: the basic meaning of something; the crucial part

from The Collaborative International Dictionary of English v.0.48

omega \o*me"ga\ ([=o]*m[=e]"g[.a] or [=o]*m[=a]"g[.a] or
   [=o]"m[-e]*g[.a]; 277), n. [NL., fr. Gr. 'w^ me`ga, i.e., the
   great or long o. Cf. {Mickle}.]
   1. The last letter of the Greek alphabet. See {Alpha}.
      [1913 Webster]

   2. The last; the end; hence, death.
      [1913 Webster]

            "Omega! thou art Lord," they said.    --Tennyson.
      [1913 Webster]

   {Alpha and Omega}, the beginning and the ending; hence, the
      chief, the whole. --Rev. i. 8.
      [1913 Webster]

            The alpha and omega of science.       --Sir J.
                                                  Herschel.
      [1913 Webster]