Humus is the stable form of soil organic matter derived from decomposition of plant and animal substances. Humic layer or humus horizon is the organic matter above the topsoil and below leaf litter which is finely divided having a high surface area. This layer consists of a large proportion of humus. Humus can be found in many layers of the soil, but usually in the upper layers. Humus, which ranges in colour from brown to black, is largely composed of carbon, and contains high amounts of nitrogen, and smaller amounts of phosphorus and sulfur. Humus retains moisture in the topsoil, in particular in soils with a coarse texture. Humus is the Latin word for "ground" or "earth".