Taxonomy :
Taxis= arrangement, nomos= law -> Taxonomy is the study of principles and procedures of classification.
This word proposed by A.P. de. Candolle in his book "Theories elementaire de Ia botanique" (Theory of elementary botany)

Taxonomy includes study of following points :
(1) Identification : A process by which an organism is recognised from the others by already known organism and is assigned to a particular taxonomic group is called identification.
(2) Nomenclature : Naming of organism according to international scientific rules is called nomenclature.
(3) Classification : A process by which any organism is grouped into convenient categories on the basis of
some easily observable characters.

Old Systematics :-
(1) The terrn "Systematics" was proposed by Linnaeus. The word systematics is derived from the latin word "systema'' which means systematic arrangement of organisms.
(2) According to G. Simpson : Systematics is the study of diversity of organisms and all their comparative and evolutionary relationship.
Note : It includes description of external morphological characters of plants or living organisms.
eg- Morphological characters of Root,Stem,Leaves,Flowers.

New systematics or Neo systematics :-
(1) Neo - systematics - A new branch - Name given by Julian Huxley (1940)
(2) It includes description of all external and internal structure along with the structure of cell, development process and eclogical informations of organisms.
(3) It is used to know the inter relationship among living organism.
Note : New systematics is mainly based on evolutionary as well as genetic relationship(experimental taxonomy) as compared to morphological characters.