Triskaidekaphobia is the fear of the number 13. It's not exactly classified as a phobia because it's neither an object nor a situation. Many scientists call it an irrational fear. This phobia is common among Christians but not limited to them. It's feared because of two instances in the Christian mythology: Jesus' last supper where there were 13 people and his crucifixion on Friday the 13th. There is also an unpopular reason for this fear: In medieval times, 13 steps were leading to the gallows, where the person would later lose his/her life.
Now, coming to how this makes a person react to the number 13 is interesting. The people affected by this phobia find that their fears rise only under certain situations, and it is different for all of them. It's almost impossible to escape this fear because one can not avoid the number 13 all the time. To avoid the arousal of this fear among people western hotels skip the 13th floor, some airlines skip the 13th row and some towns skip the 13th street.
There is yet another superstition related to the number 13. This time it's Friday the 13th it's considered a really unlucky day, because of this many movie franchises do not release movies on Friday the 13th. It is not just considered an unlucky day because of Jesus' crucifixion but also because once a movie franchise lost over a million dollars because of a film they released on Friday the 13th.
So the next time someone tells you that they fear the number 13 instead of telling them it's irrational just tell them that the fear is justified because of its unlucky history :).
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