Stazionario

Stazionario is an Italian term used mainly in scientific and technical contexts to describe something that does not change with time. The word derives from stazione and its sense is close to the English stationary or steady-state. In general, it characterizes quantities, processes, or systems whose statistical properties or behavior remain constant over time.

In mathematics and statistics, the expression processo stazionario refers to a stochastic process whose probabilistic characteristics do not depend on the time at which it is observed. Commonly, this means that the mean and the autocovariance are time-invariant. The concept is central to time series analysis and signal processing, where stationary models provide a simpler framework for inference and prediction. The term can also describe stationary noise, whose statistical traits do not vary with time.

In physics, engineering, and related fields, stazionario is used to describe physical states or flows that reach a steady condition. For example, a flusso stazionario (steady flow) in fluid dynamics is one in which the flow properties at any given point do not change over time. A system in stato stazionario (steady state) has outputs and internal variables that settle to constant values or to residues that do not evolve further.

Inflection and usage notes: stazionario is the masculine singular form; feminine is stazionaria, plural stazionari or stazionari, depending on gender. It is commonly used with nouns such as processo, rumore, stato, flusso, and sistema.

See also: stationary process, steady state, time series analysis, steady-state theory.