1. Soils which are composed primarily of organic materials.

Most Histosols are formed in settings; such as, wetlands where restricted drainage diminishes the decomposition of plant and animal remains, allowing these organic materials to accumulate over time.

Histosols are often referred to as peats and mucks which are mined for fuel and horticultural products.

Histosols are divided into five suborders: Folists, Wassists, Fibrists, Saprists, and Hemists all of which are defined in other word entries of this unit.

2. From the U.S. Soil Taxonomy soil-order classification system.
3. Etymology: from Greek histos, "tissue".