Cohesion

Cohesion is the action or property of forming a united, coordinated whole. In everyday use it describes the bonds that bind objects or parts together, while in specialized fields it denotes the forces or design principles that keep components operating as a single system. The concept is used across social sciences, natural sciences, linguistics, and information technology to compare how tightly related or interdependent elements must be.

In sociology and related disciplines, social cohesion refers to the bonds that hold a community together, including trust, shared norms, and institutions that support cooperation and social solidarity. In materials science and physics, cohesion describes the internal forces that hold a substance’s particles together, such as ionic, covalent, and metallic bonds, or cohesive intermolecular forces like van der Waals interactions. These forces influence strength, toughness, and properties such as surface tension. Cohesion is often contrasted with adhesion, which concerns attraction between unlike substances.

In linguistics and textual analysis, cohesion refers to the devices that link sentences and parts of a text so it reads as a coherent whole. This includes pronouns, demonstratives, conjunctions, lexical repetition, and referential ties. Cohesion contributes to coherence, the overall clarity and meaningfulness experienced by a reader or listener.

In computing and software engineering, cohesion describes how closely the responsibilities of a module or component align with a single purpose. High cohesion indicates that elements within a module fit together well, improving maintainability, testability, and reuse; low cohesion signals mixed responsibilities. Cohesion is frequently discussed alongside coupling, which measures interdependencies between modules.