koodiyksikön

The koodiyksikön is a Finnish term used in software development to describe a discrete code element that encapsulates a portion of functionality and exposes a defined interface. A code unit can be developed, tested, deployed, and replaced independently within a larger software system.

Its boundaries are determined by responsibilities and interfaces rather than by file boundaries alone. A code unit typically includes internal implementation details that are hidden behind a contract, such as a function signature, a module export, or a class interface. Dependencies on other units are minimized and explicit, enabling easier testing and reuse.

In practice, a koodiyksikön can correspond to a function, a class, a module, a library, or, in more coarse-grained architectures, a service or component. The term is used flexibly across languages and paradigms, reflecting granularity decisions rather than a fixed size. Common activities around a code unit include unit testing, versioning, documentation, and ensuring compatibility with its interface.

Derived from koodi (code) and yksikkö (unit), the concept is common in Finnish-language software engineering literature, but there is no single formal standard; dependent on context, the same term may describe different levels of granularity. See also: module, component, function, service.