The Collaborative International Dictionary of English v.0.48:

Apothecary \A*poth"e*ca*ry\, n.; pl. Apothecaries. [OE.
   apotecarie, fr. LL. apothecarius, fr. L. apotheca storehouse,
   Gr. apo, fr. ? to put away; ? from + ? to put: cf. F.
   apothicaire, OF. apotecaire. See Thesis.]
   1. One who prepares and sells drugs or compounds for
      medicinal purposes; a druggist; a pharmacist.
      [1913 Webster]

   Note: In England an apothecary is one of a privileged class
         of practitioners, licensed to prescribe medicine -- a
         kind of sub-physician. The surgeon apothecary is the
         ordinary family medical attendant. One who sells drugs
         and makes up prescriptions is now commonly called in
         England a druggist or a pharmaceutical chemist.
         [1913 Webster]

   2. A drugstore; a store where medicines are sold.
      [PJC]

   Apothecaries' weight, the system of weights by which
      medical prescriptions were formerly compounded. The pound
      and ounce are the same as in Troy weight; they differ only
      in the manner of subdivision. The ounce is divided into 8
      drams, 24 scruples, 480 grains. See Troy weight.
      [1913 Webster]