Restrict

Restrict is a verb meaning to limit, confine, or impose conditions on something. The word comes from the Latin restringere, meaning to draw back or bind. In common usage, to restrict something is to set boundaries on its use, access, scope, or occurrence.

In everyday language, restrictions appear in various forms. Travel restrictions limit who may move across borders or within regions. Access restrictions control who can reach a building, system, or document. Usage restrictions specify how a product or resource may be used, and legal restrictions are rules enacted by governments or organizations to regulate behavior or activities.

In mathematics and related fields, restriction refers to focusing a concept on a subset of a larger structure. For example, restricting a function means taking its values only on a subdomain and considering the restricted function as a map from that subdomain to its codomain. Restrictions also apply to measures, subspaces, or other objects when attention is limited to a subcollection or substructure.

In computer science, restrict is a keyword in the C99 programming language. The restrict qualifier indicates that for the lifetime of the pointer, the object it points to is not accessed through any other pointer, enabling certain optimizations by the compiler. Similar concepts exist in databases and access control, where permissions and policies restrict who can view or modify data.

Restriction, as a noun, denotes the act of restricting or a rule that limits behavior or access. See also constraint, limitation, and regulation.