The book Systema Naturæ (commonly written Systema Naturae without the ligature æ in modern English) was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735. The full title of the 10th edition, which was certainly the most important one, was Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis or translated: "System of nature through the three kingdoms of nature, according to classes, orders, genera and species, with characters, differences, synonyms, places".
The tenth edition of this book is considered the starting point of zoological nomenclature.
Linnaeus (later known as "Carl von Linné", after his ennoblement in 1761) published the first edition of Systema Naturae in the year 1735, during his stay in the Netherlands. As customary for the scientific literature of its day, the book was published in Latin. In it, he outlines his ideas for the hierarchical classification of the natural world, dividing it into the animal kingdom (Regnum animale), the plant kingdom (Regnum vegetabile) and the "mineral kingdom" (Regnum lapideum).
At the time of Linnaeus only about 10,000 species of organisms were recognized by science, about 6,000 species of plants and 4,236 species of animals. Even in 1753 he believed that the number of species of plants in the whole world would hardly reach 10,000; in his whole career he named about 7,700 species of flowering plants.
The classification of the plant kingdom in the book was not one meant to reflect the actual order of nature but to organize it in a fashion convenient for humans: it followed Linnaeus' new sexual system where species with the same number of stamens were treated in the same group. Linnaeus believed that he was classifying God's creation and was not trying to express any deeper relationships. He is frequently quoted to have said God created, Linnaeus organized. The classification of animals was more natural. For instance, humans were for the first time placed together with other primates, as Anthropomorpha.
In view of the popularity of the work, Linnaeus kept publishing new and ever-expanding editions, growing from eleven very large pages in the first edition (1735) to 1400 pages in the twelfth edition (1766/1767). Also, as the work progressed he made changes: in the first edition whales were classified as fishes, following the work of Linnaeus' friend and "father of ichthyology" Peter Artedi; in the 10th edition, published in 1758, whales were moved into the mammal class. In this same edition he introduced two part names (see binomen) for animal species, something he had done for plant species (see binary name) in the 1753 publication of Species Plantarum. The system eventually developed into modern Linnaean taxonomy, a herarchically organized biological classification.