Abstract is: Nudity is the state of being in which a human is without clothing. Nudity is culturally complex due to meanings given to various states of undress in differing social situations. In any particular society, these meanings are defined in relation to being properly dressed, not in relation to the specific body parts being exposed. Although often used interchangeably, "naked" and "nude" are also used in English to distinguish between the various meanings of being unclothed. Nakedness and clothing are connected to many cultural categories including identity, social status and moral behavior. Contemporary social norms regarding nudity vary widely, reflecting cultural ambiguity towards the body and sexuality, and differing conceptions of what constitutes public versus private spaces. While the majority of societies require clothing in most situations, others recognize non-sexual nudity as being appropriate for some recreational, social or celebratory activities, and appreciate nudity in the arts as representing positive values. Societies such as Japan and Finland maintain traditions of communal nudity based upon the use of baths and saunas that provided alternatives to sexualization. Some societies and groups continue to disapprove of nudity not only in public but also in private based upon religious beliefs. Norms are codified to varying degrees by laws defining proper dress and indecent exposure. The loss of body hair was one of the physical characteristics that marked the biological evolution of modern humans from their hominin ancestors. Adaptations related to hairlessness contributed to the increase in brain size, bipedalism, and the variation in human skin color. While estimates vary, for at least 90,000 years anatomically modern humans wore no clothing, the invention of which was part of the transition from being not only anatomically but behaviorally modern. Through much of history until the early modern period, people were unclothed in public by necessity or convenience either when engaged in effortful activity, including labor and athletics; or when bathing or swimming. Such functional nudity occurred in groups that were usually but not always segregated by sex. In the colonial era Christian and Muslim cultures more frequently encountered Indigenous peoples who used clothing for decorative or ceremonial purposes but were often nude, having no concept of shame regarding the body. Social norms relating to nudity are different for men than they are for women. Individuals may intentionally violate norms relating to nudity; those without power may use nudity as a form of protest, and those with power may impose nakedness on others as a form of punishment.