a b c book

from The Collaborative International Dictionary of English v.0.48

A B C \A B C"\ ([=a] b[=e] s[=e]").
   1. The first three letters of the alphabet, used for the
      whole alphabet.
      [1913 Webster]

   2. A primer for teaching the alphabet and first elements of
      reading. [Obs.]
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   3. The simplest rudiments of any subject; as, the A B C of
      finance.
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   {A B C book}, a primer. --Shak.
      [1913 Webster]