An aggregate is a broad category of coarse- to medium-grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete, and geosynthetic aggregates. Aggregates are the most mined materials in the world and are used as a component of composite materials such as concrete and asphalt, where they serve as reinforcement to add strength to the overall composite material. Aggregates are also used as a stable foundation or road/rail base with predictable, uniform properties, or as a low-cost extender that binds with more expensive cement or asphalt to form concrete.

In addition to its use in construction, "aggregate" can also be used as a verb to mean "to collect or gather into a mass or whole". It can also be used as an adjective to describe something that is formed by the collection of units or particles into a body, mass, or amount. As a noun, "aggregate" can refer to a mass or body of units or parts somewhat loosely associated with one another.

Furthermore, in the context of insurance, an "aggregate limit" refers to the maximum amount an insurer will pay for all claims made against the insured during the policy period, regardless of the number of separate claims made. The aggregate limit applies to both indemnity payments and defense costs incurred on the insureds behalf, and when the cumulative sum of all the payments an insurer has made during a single policy period exceeds the aggregate limit, the policys coverage is exhausted.