In Western cultures the number 13 is associated with superstition that can range from minor to severe. In the Far East number 4 has similar connotations.
Triskaidekaphobia: fear of the number 13
Paraskevidekatriaphobia: fear of Friday the 13th
Several possible origins have been proposed for each, but no one will know the reason for sure. One theory is that 12 was the perfect number in antiquity, so 13 became associated with imperfection.
Some people view these as a sign of bad luck. Others develop a phobia that can be paralyzing.
Some consequences of the superstition:
(1) lack of a 13th floor in a building
(2) lack of a 13 in a series
(3) avoidance of activities on that date (weddings, meetings, etc)
(4) full-blown phobia
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