Why Is The Number 13 Thought To Be Unlucky?

The number thirteen is thought to be unlucky in many cultures. Fear of the number 13 is called 'triskaidekaphobia'. Due to this fear, tall buildings have actually skipped the 13th floor, either by numbering it '14', or labelling the floor as '12a'. Some streets also missed out the house number 13.

The number 13 is also considered unlucky in months, when it falls on a particular day. Friday the 13th is one, and fear of this is called 'paraskavedekatriaphobia' or 'friggatriskaidekaphobia'.

One interpretation as to why it is unlucky is because there are 13 full moons in a year, and a women who live in a natural environment tend to have their period during a full moon. In the past, women who 'bled' during the full moon were seen as witches.

The number 13 is seen lucky in some cases however. A small number of left handers consider it to be lucky, and also people who are born on the 13th day of a month.