Contain

Contain is a verb with several related meanings centered on holding, enclosing, or limiting something within boundaries or a space. In its most common sense, to contain means to hold something within a container or inside a defined area: for example, a bottle contains water or a box contains books. It can also mean to include as part of a whole: a booklet that contains multiple chapters or a report that contains several recommendations.

As a verb of restraint, contain can mean to control or suppress a force, emotion, or outbreak: authorities may try to contain a crowd or efforts to contain the spread of a disease. In safety and public health contexts, containment refers to measures designed to prevent expansion or transmission. In everyday language, to contain can also imply keeping something under limits or within set boundaries, such as containing costs or containing anger.

In mathematics and logic, contain describes a relation between sets, where set A contains set B if B is a subset of A.

Etymology traces contain to the Latin continere, meaning to hold together, from com- “together” and tenēre “to hold.” Related forms include containment, the act or policy of containing, and container, a vessel that holds contents.

Usage notes: contain is a transitive verb and typically requires an object. It is often interchangeable with hold in physical sense but retains distinct nuance when referring to inclusion, restriction, or prevention. The term is widely used across everyday language, science, law, and policy to describe holding, including, restraining, or preventing movement or spread.