Hygiene is the maintenance of healthy practices. In modern terminology, this is usually regarded as a particular reference to cleanliness. The term Hygiene originates as a reference to Hygieia, who was a daughter of Asclepius and the goddess of health, cleanliness and sanitation. The related term personal grooming/grooming means to enhance one's physical appearance or appeal for others, by removing obvious imperfections in one's appearance or improving one's hygiene.

Outward signs of good hygiene include the absence of visible dirt (including dust and stains on clothing) or of bad odor/smells. Since the development of the germ theory of disease, hygiene has come to mean any practice leading to the absence of harmful levels of bacteria.

Good hygiene is an aid to health, beauty, comfort, and social interactions. It directly aids in disease prevention and/or disease isolation. (That is, good hygiene will help keep one healthy and thus avoid illness. If one is ill, good hygiene can reduce one's contagiousness to others.)