The word soil may be used to describe either a substance (or material) composed of minerals, organic matter, liquids, and gases or a three-dimensional natural body that is composed of soil materials and changes over time due to pedogenesis. In this paper, the historical and current context of these dual concepts of soil will be discussed as applied to quantitative and tacit knowledge-based methods of soil resource assessment and to communication across audiences. The soil as a substance concept is expressed by using soil as a non-countable noun as in “What is soil?”. The non-countable usage is the most widely used, partially because many non-soil scientists understand the concept of soil as a substance but not as a natural body. To express the soil as a natural body concept, we use the countable noun form as in “What is a soil?”. The plural form, soils, is identical for the non-countable and countable noun forms, though the meaning is different: multiple soil materials versus multiple soil bodies. As a collective noun, the soil is used to represent the aggregate of all soil bodies on the earth's surface, a term analogous to pedosphere. However, the soil may also be used to reference a specific soil material or soil body, and is therefore ambiguous unless made clear by the context of the usage. Some speakers also use the non-countable form soil to represent all soil materials. The concept of soils as natural bodies implies the existence of soil individuals. Soils exist along a continuum with diffuse to abrupt vertical and lateral transitions. Humans can perceive similarities and differences between soil bodies, as we can with all objects, using tacit knowledge gained through observation of soil morphology and function. In the United States, tacit knowledge has been integrated into soil survey through the use of soil series to name soils at the local scale. Adjectives such as “good” and “bad” are used to specify how well a given pedon or soil body matches the speaker's modal concept of that series. An extended apprenticeship is required for a field soil scientist to gain a sufficient level of tacit knowledge to apply soil series for soil mapping within the National Cooperative Soil Survey program. Natural resource assessment methods will be analyzed to determine whether they estimate the quantities and properties of soil materials in a given landscape or delineate and describe soil bodies. Historical and contemporary texts will be analyzed for the use and misuse of the noun forms for soil. Implications of the concepts of soil as a substance versus a soil as a natural body will be discussed for resource assessment and communication across audiences. I will argue that since the countable form encompasses the non-countable form (a soil is composed of soil), the countable form should be used when discussing soils generally or when discussing soil bodies and the non-countable form should be restricted to specific discussion of soil materials. Problems associated with the collective noun form, the soil, will be discussed as related to education and communication.