Week/wiːk/ Definition 1 of 3Pro Tip 1/3International Variations Start days for 'week' vary globally; some countries consider Sunday the first day. In the US, calendars show the week starting on Sunday. Pro Tip 2/3Flexible Start Days Weeks can begin on any day for specific needs; it's not limited to Monday or Sunday. Our work week starts on Wednesday this week. Pro Tip 3/3Contextual Use Specify 'next' or 'last' week for clarity when discussing past or future events. She visited last week, not this week.