Source : Webster's Revised Unabridged Dictionary (1913)

Chemistry \Chem"is*try\ (k[e^]m"[i^]s*tr[y^]; 277), n. [From
   {Chemist}. See {Alchemy}.]
   1. That branch of science which treats of the composition of
      substances, and of the changes which they undergo in
      consequence of alterations in the constitution of the
      molecules, which depend upon variations of the number,
      kind, or mode of arrangement, of the constituent atoms.
      These atoms are not assumed to be indivisible, but merely
      the finest grade of subdivision hitherto attained.
      Chemistry deals with the changes in the composition and
      constitution of molecules. See {Atom}, {Molecule}.

   Note: Historically, chemistry is an outgrowth of alchemy (or
         alchemistry), with which it was anciently identified.

   2. An application of chemical theory and method to the
      consideration of some particular subject; as, the
      chemistry of iron; the chemistry of indigo.

   3. A treatise on chemistry.

   Note: This word and its derivatives were formerly written
         with y, and sometimes with i, instead of e, in the
         first syllable, chymistry, chymist, chymical, etc., or
         chimistry, chimist, chimical, etc.; and the
         pronunciation was conformed to the orthography.

   {Inorganic chemistry}, that which treats of inorganic or
      mineral substances.

   {Organic chemistry}, that which treats of the substances
      which form the structure of organized beings and their
      products, whether animal or vegetable; -- called also
      {chemistry of the carbon compounds}. There is no
      fundamental difference between organic and inorganic
      chemistry.

   {Physiological chemistry}, the chemistry of the organs and
      tissues of the body, and of the various physiological
      processes incident to life.

   {Practical chemistry}, or {Applied chemistry}, that which
      treats of the modes of manufacturing the products of
      chemistry that are useful in the arts, of their
      applications to economical purposes, and of the conditions
      essential to their best use.

   {Pure chemistry}, the consideration of the facts and theories
      of chemistry in their purely scientific relations, without
      necessary reference to their practical applications or
      mere utility.

Source : WordNet®

chemistry
     n 1: the science of matter; the branch of the natural sciences
          dealing with the composition of substances and their
          properties and reactions [syn: {chemical science}]
     2: the way two individuals relate to each other; "their
        chemistry was wrong from the beginning -- they hated each
        other"; "a mysterious alchemy brought them together" [syn:
         {interpersonal chemistry}, {alchemy}]