Sterilisation, sterilisation and sterilisation are processes by which materials and objects are freed from living microorganisms including their resting stages (e.g. spores). The state of the materials and objects thus achieved is referred to as "sterile".

The term "germ-free", which is also used instead of "sterile", is incorrect because sterilisation does not only involve the removal or killing of certain developmental stages of microorganisms, namely germs, but the removal or killing of all microorganisms in every developmental stage. The term "germ-free" is related to the misnomer "germ" for microorganisms in every stage of development.

Sterilisation of materials (e.g. food, pharmaceuticals, solutions), medical instruments, implants, objects, packaging, devices (e.g. endoscopes) and vessels (e.g. for the culture of microorganisms) (ideally) kills all microorganisms contained or adhering to them, including their permanent forms (for example spores), and destroys viruses, prions (infectious proteins), plasmids and other DNA fragments.

In practice, complete sterilisation does not succeed with 100% certainty. Therefore, a reduction of the number of microorganisms capable of multiplication by a factor determined according to the area of application (in powers of ten) or a certain probability of complete sterilisation is required. For example, it is required that the residual content of reproducible microorganisms in a unit of the sterilisation material is at most 10', i.e.: only one reproducible microorganism may be contained in one million equally treated units of the sterilisation material.

Sterilisation is carried out by physical (thermal, irradiation) or chemical processes. In the technical distinction from disinfection, sterilisation usually requires a probability of complete sterilisation that is one power of ten higher.

Source: https://de.wikipedia.org/wiki/Sterilisation