the act of classifying.

the result of classifying or being classified.

one of the groups or classes into which things may be or have been classified.

Biology . the assignment of organisms to groups within a system of categories distinguished by structure, origin, etc. The usual series of categories is phylum (or, esp. in botany, division ), class, order, family, genus, species, and variety.

the category, as restricted, confidential, secret, or top secret, to which information, a document, etc., is assigned, as by a government or military agency, based on the degree of protection considered necessary to safeguard it from unauthorized use.

Library Science . any of various systems for arranging books and other materials, esp. according to subject or format.

noun

allocation , alloting , allotment , analysis , apportionment , arrangement , assignment , assortment , cataloguing , categorizing , codification , collocation , consignment , coordination , denomination , department , designation , disposal , disposition , distributing , distribution , division , echelon , gradation , grade , grading , graduation , group , grouping , kind , order , ordering , ordination , organization , pigeonholing , regulation , sizing , sorting , systematization , tabulating , taxonomy , typecasting , categorization , deployment , formation , layout , lineup , placement , sequence , category , set , confidential , family , file , genre , genus , niche , rank , rate , rating , sort , species , system