Taxonomy (from Greek τάξις, taxis, ‘arrangement’, and -νομία, -nomia, ‘method’) is the science of classifying organisms and assigning them to taxonomic units (such as genera, families and orders). Organisms are classified into groups based on similarities of characteristics or traits. Biologists use a hierarchical system to classify organisms. In this system, each level is more general than the next. The most general grouping is kingdom. There are six kingdoms: bacteria, archaea, protists, fungi, plants and animals.
The classification of organisms into groups is called taxonomy. Taxonomists use a variety of methods to group organisms including: morphology (form and structure), physiology (biochemical and physiological features), ecology (the way an organism interacts with its environment), development (embryological changes) and genetics (DNA).
There are different ways of ranking the groups within each kingdom. For example, in the animal kingdom there are phyla (singular: phylum). The largest grouping within a phylum is a class; examples include mammals, reptiles and birds. Within each class there are smaller groups called orders; for example primates (which includes apes, monkeys and humans) is an order within the class Mammalia. Each order contains one or more families; for example Hominidae (which includes gorillas, chimpanzees and humans) is a family within the order Primates. Finally, each family contains one or more genera; for example Homo (which includes Homo sapiens – modern humans) is a genus within the family Hominidae.”