This document discusses soil structure, including the definition of soil structure as the arrangement of primary soil particles into aggregates called peds. Different types of soil structures are described such as granular, blocky, prismatic, and massive. Soil structure influences properties like density, porosity, permeability and strength. Good soil structure facilitates water and air movement while poor structure restricts it. Soil structure can be altered by tillage or compaction, which can break down natural aggregates. Bulk density, porosity and their relationship to particle density are also covered.