Cleanliness in the context of Cleaning

Ritual purification is a ritual prescribed by a religion through which a person is considered to be freed of uncleanliness, especially prior to the worship of a deity, and ritual purity is a state of ritual cleanliness. Ritual purification may also apply to objects and places. Ritual uncleanliness is not identical with ordinary physical impurity, such as dirt stains; nevertheless, body fluids are generally considered ritually unclean.

Most of these rituals existed long before the germ theory of disease, and figure prominently from the earliest known religious systems of the Ancient Near East. Some writers connect the rituals to taboos.

In engineering, a housing or enclosure is a container, a protective exterior (e.g. shell) or an enclosing structural element (e.g. chassis or exoskeleton) designed to enable easier handling, provide attachment points for internal mechanisms (e.g. mounting brackets for electrical components, cables and pipings), maintain cleanliness of the contents by shielding dirt/dust, fouling and other contaminations, or protect interior mechanisms (e.g. delicate integrated electrical fittings) from structural stress and/or potential physical, thermal, chemical, biological or radiational damages from the surrounding environment. Housing may also be the body of a device, vital to its function.

A stain is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon. They are caused by the chemical or physical interaction of two dissimilar materials. Accidental staining may make materials appear used, degraded or permanently unclean. Intentional staining is used in biochemical research, and for artistic effect, such as in wood staining, rust staining and stained glass.