Taxonomy is the practice and science of classification. The word is also used as a count noun: a taxonomy, or taxonomic scheme, is a particular classification. The word finds its roots in the Greek language , taxis (meaning 'order', 'arrangement') and , nomos ('law' or 'science'). Originally taxonomy referred only to the classifying of organisms or a particular classification of organisms. In a wider, more general sense, it may refer to a classification of things or concepts, as well as to the principles underlying such a classification. Taxonomy is different from meronomy which is dealing with the classification of parts of a whole.