undefiniert

Undefiniert is a German adjective meaning not defined or lacking a defined value. It is used across several fields, including mathematics, logic, computing, philosophy, and everyday language, to indicate that a concept or quantity has no determinate meaning within a given system.

In mathematics, undefined expressions occur when a value cannot be assigned by the rules in use. Examples include division by zero (such as 1/0 in the real number system), the square root of a negative number in the real numbers, or the logarithm of non-positive numbers. A function may be undefined at points where its formula does not produce a value, as with f(x)=1/x at x=0. In calculus and analysis, the term undefined is sometimes distinguished from indeterminate or unbestimmte forms, which require further analysis to resolve.

In computing, undefined behavior (undefiniertes Verhalten) describes operations whose result is not specified by the programming language standard. Such behavior can vary between compilers or platforms and may lead to crashes, incorrect results, or security vulnerabilities. Examples include using uninitialized memory, signed integer overflow, or accessing memory outside array bounds.

In logic and geometry, some terms are regarded as undefined or primitive notions (undefinierte Begriffe). These concepts are not defined in terms of other concepts but are stated axiomatically or taken as intuitive notions, such as point or line in Euclidean geometry.

Across contexts, undefiniert often signals missing, unknown, or inapplicable values, including in data, documentation, and everyday speech.