Densities refer to the degree of compactness or relative heaviness of a substance. There are several synonyms for this term, including thickness, consistency, concentration, compression, and viscosity. Thickness is commonly used to describe the density of a substance or material. Consistency refers to how thick or thin a substance is and is often used to describe food products. Concentration refers to the amount of a particular substance in a mixture, while compression describes how tightly packed a material is. Finally, viscosity is a measure of how easily a substance flows and is often used to describe liquids. These synonyms are useful for describing different qualities and characteristics of density in various contexts.