Week

A week is a time unit equal to seven days. It is the standard time period used for cycles of work days and rest days in most parts of the world, mostly alongside (but not strictly part of) the Gregorian calendar.

The days of the week were named in different languages after classical planets, various deities (example: Thursday – Thor's day, a variation after Jupiter's day from Roman times) and heavenly bodies (example: Sunday – Sun's day) and other sources. In English, the names are Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday.

ISO 8601 includes the ISO week date system, a numbering system for weeks within a given year – each week begins on a Monday and is associated with the year that contains that week's Thursday (so that if a year starts in a long weekend Friday–Sunday, week number one of the year will start after that).

The term "week" is sometimes expanded to refer to other time units comprising a few days, such as the nundinal cycle of the ancient Roman calendar.