Triskaidekaphobia is the intense fear of the number thirteen. Triskaidekaphobia is why some architects design buildings without a thirteenth floor.
Triskaidekaphobia is made of four ancient Greek components: tris, three; kai, and; deka, ten; and phobos, fear. That adds up: seventeen characters, minus 4 Greek components...that’s 13! Superstition, you say? A phobia, as opposed to a fear, is often very specific and very extreme. It is not a phobia to fear fire; it is a phobia to fear clowns (and the number thirteen).