Canada does have marathons. Canadians too fight for deadly disease
What percent of the world's population runs marathons?
The same as marathons anywhere else: 26.2 miles.
Egypt did not have marathons, this is a product of modern sports.
Everywhere
The cast of Marathons for Mandela - 2013 includes: Eddie Izzard as himself
Berlin and London.
The Whiskey Row Marathon races are held on the first Saturday in May in Prescott, AZ
Yes, they do.
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No, marathons is a plural noun. The singular form may be used as a noun adjunct (e.g. marathon runner).
Assuming you mean long distance running marathons, the marathon was one of the original modern Olympic events that took place in 1896.