Abstract: Despite the more than one hundred years history of soil science, its object is still not clearly and unambiguously defined. Different definitions of soil can be found in the scientific literature and manuals. Uncertainty of this term, even in the scientific environment, leads to underestimation of practical significance of soil science as a science and to misunderstanding of the term "soil" both by related specialists and the general population. The accumulated factual data and the whole experience of soil science allow at this stage to make an attempt to clarify its basic concepts, including the object of research. The subject of research is the soil science and clarification of its definition in order to specify the concept of "soil" as an isolated natural body. Analysis of existing definitions of soil served as a basis for formulating a new definition of soil as an isolated natural body. An alternative view of soil as an isolated natural body is presented. It is proposed to consider soil as a natural body formed as a result of transformation of wastes of organic life on the planet and related processes under the influence of external conditions. From this point of view many properties and functions of soil should be reinterpreted. The proposed definition allows us to position soil as an isolated natural body that is a link in the single global cycle of life on Earth: in the process of soil formation, waste products of plants, animals, microorganisms, and humans are transformed into soil, which in turn ensures the reproduction and existence of life by feeding and growing plants (soils fertility function) as the beginning of all major trophic chains on the planet.