Time is a dimension in which events can be ordered from the past through the present into the future, and also the measure of durations of events and the intervals between them. Time has long been a major subject of study in religion,philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently eluded scholars. Nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective measuring systems. Some simple, relatively uncontroversial definitions of time include "time is what clocks measure" and "time is what keeps everything from happening at once".
A home is a dwelling-place used as a permanent or semi-permanent residence for an individual, family, household or several families in a tribe. It is often a house, apartment, or other building, or alternatively a mobile home, houseboat, yurt or any other portable shelter. Larger groups may live in a nursing home, children's home, convent or any similar institution. A homesteadalso includes agricultural land and facilities for domesticated animals. Where more secure dwellings are not available, people may live in the informal and sometimes illegal shacks found in slums and shanty towns. More generally, "home" may be considered to be a geographic area, such as a town, village, suburb, city, or country.
Transitory accommodation, such as a hospital, prison, boarding school, college or university is not normally considered permanent enough to replace a more stable location as 'home'. In 2005, some 100 million people worldwide were estimated to be homeless, although some prefer the term 'houseless' or 'unsheltered'.