• physical: time interval in which half of the nuclei of a radioactive nuclide have decayed. Short half-lives lead to a high radiation activity, long half-lives yield a low radiation activity.
• biological: time interval in which a biological system, e.g. a human being or an animal, excretes (e.g. via the urine) half of the amount of a certain substance taken up in the body or a certain organ.
• effective: time interval in which the amount of a radionuclide in a biological system is reduced by half, as a result of a coaction of radioactive decay and excretion.

Driving of cavities (mining).

In epidemiological cohort studies a low frequency of falling ill often occurs in occupationally exposed groups of persons, compared to non-exposed persons of the general population, as for some professions a certain health constitution is a prerequisite. Not employed persons are usually "more ill" than employed persons. A reduced risk of falling ill based on the unilateral selection of healthier occupationally exposed persons is referred to as Healthy Worker Effect.

High-frequency electromagnetic fields. Here defined as frequencies between 100 kHz and 300 GHz.

Helmholtz Zentrum München- German Research Center for Environmental Health

The horizontal pillar is the mining term for the remaining rock between superposing mine openings.

Strongly shielded, tight housing where radioactive materials of high activity are handled by remote control with the help of manipulators and where work processes can be observed through leaded windows, thus not involving risks for the staff.

Spatially limited areas with particularly high absorption of electromagnetic fields.

Representative selection of households where interviews have been carried out in intervals.