Triskaidekaphobia is frequently defined as the fear of the number 13. More accurately, triskaidekaphobia refers to superstitions about the unlucky nature of the number of 13. These superstitions are common in the US and in England, but they are certainly not global. Instead of triskaidekaphobia, many Asian countries have superstitions related to the number 4, called tetraphobia.
Friday the 13th is considered particularly unlucky, and a person who fears that date occurring, rather than simply the number 13 suffers from paraskavedekatriaphobia or friggatriskaidekaphobia. Whether you fear the number or the date, there are several reasons why the date is considered unlucky.
It is believed that triskaidekaphobia had to emerge after Christianity, since the first unlucky association is the belief that there were 13 guests at the Last Supper of Christ. Moreover, many believe Christ was crucified on Friday the 13th. Christians later summarized that the expulsion of Adam and Eve from the Garden of Eden took place on the 13th day at the beginning of days.
Though the word, triskaidekaphobia, didn’t come into use until the 19th century, the condition itself is dated to at least medieval times. Before that, some believed the number 13 was lucky. Fear of Fridays is also clearly established by the medieval period, especially because of its close association with Good Friday, the day upon which most Christians reflect on Christ’s crucifixion. Chaucer refers to misfortune falling on Friday, and references continue, becoming particularly prominent in the 17th century.
Evidence for superstition about the number 13 is gathered by numerous sources, not all of them credible. For example, many suggest Jacques de Molay, the head of the Knight’s Templar was arrested on a Friday the 13th, but this is in fact disputable. Some facts that may inspire triskaidekaphobia that are true is that there are several serial killers whose first and last names together contain 13 letters. Constantinople was sacked on Friday the 13th, but this was actually lucky for Christians involved in the crusades, and very unlucky for the residents of Constantinople.
Due to triskaidekaphobia, or especially fear of Friday the 13th, many people do not make plans or travel on that day. Beginning a journey, physically or metaphorically on that day is considered bad luck. Many will not fly on the 13th, whether or not it occurs on a Friday, and people feel that weddings, the start of vacations, and major purchases should not occur on the 13th day of any month. Triskaidekaphobia has a strong hold on the American mindset, and economists estimate an 800-900 million US dollars (USD) is lost yearly from those avoiding any business transactions on Friday the 13th.
Triskaidekaphobia has created an interesting phenomenon in many hotels and skyscrapers. They have no 13th floor, and merely skip from 12 to 14. From a rational standpoint, of course the 13th floor exists, but is relabeled as the 14th floor. Similarly, in Asian countries where people suffer from tetraphobia, hotels and skyscrapers skip the fourth floor and relabeled it as the fifth floor.