Sporadic Creutzfeldt–Jakob Disease
The qualification sporadic, indicating that occurrences of some phenomenon are rare and not systematic, can be used for: Mathematics * Sporadic group, any of a small number of finite groups that do not fit into any infinite family of groups Medicine * Sporadic disease, any of several diseases Science * Sporadic E propagation, an unusual form of radio propagation occasionally allowing long-distance communication * Sporadic meteor, not part of a meteor swarm * Sporadic permafrost Permafrost () is soil or underwater sediment which continuously remains below for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below ...

Sporadic Group
In the mathematical classification of finite simple groups, there are a number of groups which do not fit into any infinite family. These are called the sporadic simple groups, or the sporadic finite groups, or just the sporadic groups. A simple group is a group ''G'' that does not have any normal subgroups except for the trivial group and ''G'' itself. The mentioned classification theorem states that the list of finite simple groups consists of 18 countably infinite families plus 26 exceptions that do not follow such a systematic pattern. These 26 exceptions are the sporadic groups. The Tits group is sometimes regarded as a sporadic group because it is not strictly a group of Lie type, in which case there would be 27 sporadic groups. The monster group, or ''friendly giant'', is the largest of the sporadic groups, and all but six of the other sporadic groups are subquotients of it. Names Five of the sporadic groups were discovered by Émile Mathieu in the 1860s and the ot ...
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Sporadic Disease
In infectious disease epidemiology, a sporadic disease is an infectious disease which occurs only infrequently, haphazardly, irregularly, or occasionally, from time to time in a few isolated places, with no discernible temporal or spatial pattern, as opposed to a recognizable epidemic outbreak or endemic pattern. The cases are so few (single or in a cluster) and separated so widely in time and place that there exists little or no discernable connection within them. They also do not show a recognizable common source of infection.According to : "...sporadic cases do not necessarily share a single specific common contaminated source..." In the discussion of non-infectious diseases, a sporadic disease is a non-communicable disease (such as cancer) which occurs in people without any family history of that disease or without any inherited genetic predisposition for the disease (change in DNA which increases the risk of having that disease). Sporadic non-infectious diseases arise not due ...
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Sporadic E Propagation
Sporadic E (abbreviated E or SpE) is an uncommon form of radio propagation using a low level of the Earth's ionosphere that normally does not refract radio waves above about 15 MHz. Sporadic E propagation reflects signals off relatively small ionization patches in the lower E region located at altitudes of about . The more conventional forms of skywave propagation in the ionosphere's higher F region refract off layers of electrons knocked off of gas atoms and molecules by intense UV light, which are renewed on a regular repeating daily cycle. In both cases, the electrons, when present, refracts (or "bends") radio signals back toward the Earth's surface creating a "bent pipe" path for radio signals. The E propagation often supports occasional long-distance communication during the approximately 6 weeks centered on summer solstice at very high frequencies (VHF), which under normal conditions can usually propagate mostly by line-of-sight. Overview As its name ...
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Sporadic Meteor
A meteor, known colloquially as a shooting star, is a glowing streak of a small body (usually meteoroid) going through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a streak of light via its rapid motion and sometimes also by shedding glowing material in its wake. Although a meteor may seem to be a few thousand feet from the Earth, meteors typically occur in the mesosphere at altitudes from . The root word ''meteor'' comes from the Greek ''meteōros'', meaning "high in the air". Millions of meteors occur in Earth's atmosphere daily. Most meteoroids that cause meteors are about the size of a grain of sand, i.e. they are usually millimeter-sized or smaller. Meteoroid sizes can be calculated from their mass and density which, in turn, can be estimated from the observed meteor trajectory in the upper atmosphere. Meteors may occur in showers, which arise when Earth passes through a stream of debris left by ...
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