Zeitvariierten

Zeitvariierten is a German term used in technical writing to denote quantities, systems, processes, or signals that change over time. The form derives from Zeit (time) and variieren (to vary) with a past-participle ending; in practice, the adjective zeitvariiert or the noun phrase Zeitvariierten Größen is used to describe time-dependent phenomena. The concept is distinguished from time-invariant quantities that do not change with time.

In science and engineering, zeitvariierten quantities pose challenges for modeling and analysis because their behavior depends on when measurements are taken. Examples include ein zeitvariiertes Feld (a field that changes with time) in physics, or ein zeitvariables System in control theory and signal processing, where parameters, transfer functions, or inputs evolve over time. Time-varying signals in data analysis require methods that handle nonstationarity, such as time-frequency analysis.

The term is common across disciplines, though synonyms such as zeitabhängig or zeitlich variabel are also used. Some contexts prefer explicit phrases like zeitvariable Größen, zeitabhängige Größen, or zeitliche Variation. The usage reflects a broader distinction between stationary (unchanging) and non-stationary phenomena.

Related concepts include Zeitreihen (time series), Zeitinvarianz (time invariance), Dynamische Systeme (dynamic systems), and Nichtstationarität (nonstationarity).