[1] : The Collaborative International Dictionary of English v.0.48

category \cat"egory\, n.; pl. categories. l. categoria, gr.
   ?, fr. ? to accuse, affirm, predicate; ? down, against + ? to
   harrangue, assert, fr. ? assembly.
   1. logic. one of the highest classes to which the objects
      of knowledge or thought can be reduced, and by which they
      can be arranged in a system; an ultimate or undecomposable
      conception; a predicament.
      1913 webster

            the categories or predicaments -- the former a greek
            word, the latter its literal translation in the
            latin language -- were intended by aristotle and his
            followers as an enumeration of all things capable of
            being named; an enumeration by the summa genera
            i.e., the most extensive classes into which things
            could be distributed.                 --j. s. mill.
      1913 webster

   2. class; also, state, condition, or predicament; as, we are
      both in the same category.
      1913 webster

            there is in modern literature a whole class of
            writers standing within the same category. --de
                                                  quincey.
      1913 webster
see also:
categories 

[2] : WordNet (r) 2.0

category
     n 1: a collection of things sharing a common attribute; "there
          are two classes of detergents" syn: class, family
     2: a general concept that marks divisions or coordinations in a
        conceptual scheme
see also:
class family 

[3] : Moby Thesaurus II by Grady Ward, 1.0

49 moby thesaurus words for "category":
   area, blood, bracket, branch, caste, clan, class, classification,
   department, division, estate, grade, group, grouping, head,
   heading, kin, kind, label, league, level, list, listing, order,
   pigeonhole, position, predicament, race, rank, ranking, rating,
   rubric, section, sector, sept, set, sort, sphere, station, status,
   strain, stratum, subdivision, subgroup, suborder, tier, title,
   type, variety

[4] : The Free On-line Dictionary of Computing (27 SEP 03)

category
     
         a category k is a collection of objects, objk, and
        a collection of morphisms or "arrows", mork such that
     
        1. each morphism f has a "typing" on a pair of objects a, b
        written f:a->b.  this is read 'f is a morphism from a to b'.
        a is the "source" or "domain" of f and b is its "target" or
        "co-domain".
     
        2. there is a partial function on morphisms called
        composition and denoted by an infix ring symbol, o.  we
        may form the "composite" g o f : a -> c if we have g:b->c and
        f:a->b.
     
        3. this composition is associative: h o g o f = h o g o f.
     
        4. each object a has an identity morphism id_a:a->a associated
        with it.  this is the identity under composition, shown by the
        equations id_b o f = f = f o id_a.
     
        in general, the morphisms between two objects need not form a
        set to avoid problems with russell's paradox.  an
        example of a category is the collection of sets where the
        objects are sets and the morphisms are functions.
     
        sometimes the composition ring is omitted.  the use of
        capitals for objects and lower case letters for morphisms is
        widespread but not universal.  variables which refer to
        categories themselves are usually written in a script font.
     
        1997-10-06
     
     
see also:
morphisms arrows domain co-domain partial function composition 
infix set russell's paradox 

Category >> C Words
Category, definition of term: Category
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