When we talk about superstitious beliefs , the beliefs associated with Friday the 13th , no doubt , deserve a special mention . In fact , such is the fear associated with this date that people just can't seem to stick to their daily routine on this day . The data from Stress Management Center and Phobia Institute suggests that somewhere around 17 to 21 million Americans are affected by the fear associated with this day , i.e. the combination of Friday and 13 . Even worse , the financial losses caused on this day amounts to as much as US$800 million every year . As we flipped through the pages of history , we realized that Friday the 13th bears the brunt of bad luck associated with number 13 , the unluckiest number , and Friday , the unluckiest day of the week . Number 13 has always been considered unlucky , mainly as a result of it being associated with various occurrences in mythology . While some associate it with the instance of Norse mythology , in which the god of joy and gladness - Balter , was killed in a dishonest manner by Loki - the god of discord and mischief , who was the 13th guest , others associate it with the Last Supper , in which the 13th guest was Judas , who betrayed Jesus to his enemies for 30 pieces of silver . Similarly , Friday has also been a sign of bad luck to many people , with incidents like Jesus being crucified on this unfaithful day , contributing to this belief . It is also widely believed that Cain killed Able on this very day of the week . The fear of Friday the 13th is known as friggatriskaidekaphobia and paraskevidekatriaphobia , the former combining the words frigga , meaning Friday , and triskaidekaphobia , meaning the phobia of number 13 . Over the period , the belief that Friday the 13th is an unlucky day has just become one of the most widely accepted superstitions , which consequently causes much blind panic and unreasonable fear in the world . What does Friday the 13th refer to according to passage ?
The 13th Friday of a year . The fear of the number 13 on Fridays . A fixed date of a year that can bring bad luck . The 13th day of a month falling on a Friday .