Irreligion (adjective form: non-religious or irreligious) is the absence, indifference to, or rejection of religion. According to the Pew Research Center's 2012 global study of 230 countries and territories, 16% of the world's population is not affiliated with a religion, while 84% are affiliated.
Irreligion may include some forms of theism, depending on the religious context it is defined against; for example, in 18th-century Europe, the epitome of irreligion was deism, while in contemporary East Asia the shared term meaning "irreligion" or "no religion" (無宗教, Chinese pron. wú zōngjiào, Japanese pron. mu shūkyō Korean pron. mujonggyo), with which the majority of East Asian populations identify themselves, implies non-membership in one of the institutional religions (such as Buddhism and Christianity) and not necessarily non-belief in traditional folk religions collectively represented by Chinese Shendao and Japanese Shinto (both meaning "ways of gods").
According to cross-cultural studies, since religion and fertility are positively related while secularism and fertility are negatively related, secularism is expected to decline throughout the 21st century. By 2060, according to their projections, the number of unaffiliated will increase by over 35 million, but the percentage will decrease to 13% because the total population will grow faster.
The term irreligion is a combination of the noun religion and the prefix ir-, signifying "not" (similar to irrelevant). It was first attested in French as irréligion in 1527, then in English as irreligion in 1598. It was borrowed into Dutch as irreligie in the 17th century, though it is not certain from which language.