Sporadic

Sporadic is an adjective used to describe events that occur irregularly, at unpredictable intervals, or that are scattered rather than continuous or patterned. The term derives from Latin sporadicus and Greek sporadikos, from spora meaning seed, originally implying scattered sowing.

In medicine, sporadic describes disease or cases that occur irregularly and without clear clustering in families or populations. It contrasts with endemic (permanently present in a population) and epidemic (rapid, widespread) outbreaks. Examples include sporadic Creutzfeldt-Jakob disease and sporadic Alzheimer's disease, where most cases arise without a known family history.

In meteor astronomy, sporadic refers to meteors that appear randomly and are not associated with a known meteor shower. These sporadic meteors originate from dust and debris not linked to a specific parent body.

In ionospheric science, a sporadic E layer describes irregular patches of enhanced electron density in the Earth's ionosphere, which can sporadically reflect radio waves and affect radio communications.

Because of its general sense, sporadic is used across disciplines to denote irregularity or lack of pattern. It is commonly contrasted with patterned, periodic, or predictable phenomena, highlighting the absence of systematic repetition or clustering.