Also spelled paraskavedekatriaphobia, it is the abnormal and unwarranted fear or dislike of, and/or aversion to Friday the 13th.

The term is derived from triskaidekaphobia, the fear of the number 13, which comes from the Greek "tris" (three), "kai" (and), "deka" (ten) and "phobos" (fear).

"Paraskavedekatriaphobia" was coined by Dr. Donald Dossey, a psychotherapist specializing in the treatment of phobias.

Some sufferers of the phobia live with the dread of an approaching Friday the 13th hanging over them all the time. Others only experience the effects of the phobia shortly before and during Friday the 13th. The effects of the phobia (as with most phobias) range from a mild feeling of discomfort or stress to panic attacks and other physical manifestations like shortness of breath. It's believed 5-7% of Americans experience paraskavedekatriaphobia to some degree.

In Greece, the phobia is related to Tuesday the 13th, as Tuesday is considered to be the most unlucky day.

The phobia is also known as friggatriskaidekaphobia, after the goddess Frigga of Nordic mythology.