The fear of the number 13 is called triskaidekaphobia. It is a common phobia, and those who suffer from it associate the number 13 with bad luck or danger due to superstitions. People with triskaidekaphobia may avoid staying in hotel rooms with the number 13, going up to the 13th floor of any building, or sitting in the 13th row in airplanes. The fear of Friday the 13th is an extension of triskaidekaphobia and is called paraskevidekatriaphobia or friggatriskaidekaphobia.