bulk

Bulk is a term used to describe the size, mass, or volume of a substance or object as distinct from its individual units. It can refer to both physical quantities and economic concepts of large quantities. In everyday language, “in bulk” describes goods sold or stored in large quantities rather than in small packaged units.

In science and engineering, bulk properties are characteristics of a material that depend on the amount of material present and scale with volume, rather than on surface features or shape. Examples include bulk density, which is mass per unit volume including voids, and bulk modulus, a measure of incompressibility. Other bulk properties describe thermal or electrical behavior in homogeneous materials. The distinction between bulk density and true density (which excludes pore space) is a common concept in materials science and geology.

In industry and logistics, bulk refers to commodities handled in large quantities without immediate packaging. Bulk materials are stored and transported in bulk using silos, hoppers, conveyors, drums, or tankers. Bulk packaging is designed for efficiency and cost reduction, though it can complicate precise measurement, dosing, or color- and size-specific requirements. The management of bulk materials often emphasizes flow properties, moisture control, and containment to prevent loss or contamination.

In everyday use, “bulk up” means to increase size or mass, usually through growth or added nutrition. The term can also denote the main or largest part of something, as in “the bulk of the work.”