Half-life

An expression used to designate the period during which one half of a given substance decomposes, transforms, disintegrates or separates through being exposed to a particulare influence. Depending on the nature of the influence, a distinction is made between the chemical half-life (e.g. in conjunction with the Decomposition of Pesticides), the physical Half-life (Decomposition of radionuclides) and the biological half-life (e.g. the Decomposition of Organic Compounds by micro-organisms).