Final answer:
Porosity is the percentage of voids or open spaces in a rock or unconsolidated material, expressed as a percentage of the volume of open space compared to the total rock volume.
Step-by-step explanation:
The percentage of voids or open spaces in a rock or unconsolidated material is defined as porosity. Porosity is expressed as a percentage of the total volume of open space within the material compared to its total volume. Sedimentary rocks, such as those formed from well-sorted sediment, typically exhibit higher porosity due to the presence of abundant spaces between the grains. In contrast, igneous and metamorphic rocks, which have tight interlocking crystals, often have lower porosity. The concept of porosity is also vital in understanding soil composition, which can be regarded as unconsolidated material, and in water movement through substances, determining factors like aquifer productivity.