Feb 27, 2012. #6. First the easy bit: 7 year itch This is a set phrase. "You can buy a 2 week pass for the exhibition." (pass = ticket) Here " 2 week " is an adjectival phrase, and 2 week is considered to be a single period. or. "You will work your 2 weeks' notice." - Here 2 weeks' notice = "a period of notice that is of 2 weeks in length." More @Wikipedia
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