Source : Webster's Revised Unabridged Dictionary (1913)

Taxonomy \Tax*on"o*my\ (-m[y^]), n. [Gr. ta`xis an arrangement,
   order + no`mos a law.]
   That division of the natural sciences which treats of the
   classification of animals and plants; the laws or principles
   of classification.

Source : WordNet®

taxonomy
     n 1: a classification of organisms into groups based on
          similarities of structure or origin etc
     2: (biology) study of the general principles of scientific
        classification
     3: practice of classifying plants and animals according to
        their presumed natural relationships