A phobia is a type of anxiety disorder defined by an excessive and persistent fear of an object or situation. There is even one phobia called phobophobia, which is a fear of phobias.
Some common phobias:
Acrophobia - the fear of heights
Aerophobia - the fear of flying
Agoraphobia - the fear of a situation where escape may be difficult
Arachnophobia - the fear of spiders
Astraphobia - the fear of thunder and lightning
Claustrophobia - the fear of being in a small enclosed place such as a closet or an elevator
Glossophobia - the fear of public speaking
Ophidiophobia - the fear of snakes
Social phobia - social anxiety disorder
Trypanophobia - the fear of injections
The phobias listed above are the more common ones that most of us have at least heard something about, I probably have a slight form of acrophobia. I've been in many planes and tall buildings that didn't bother me, however I don't like to be up high right on the edge of something and look down such as looking straight down from the window of a tall building.
Some very unusual phobias:
Ablutophobia - the fear of bathing, if you encounter someone with this phobia you might not even have to look around to know they are in the room.
Aracibutyrophobia - the fear of peanut butter sticking to the roof of your mouth
Arithmophobia - the fear of numbers
Globophobia - the fear of balloons
Hippopotomonstrosesquippedaliophobia - the fear of long words, sesquipedalophobia is a slightly shorter word that means the same thing.
Linonophobia - the fear of string, I guess someone would have a double phobia if they saw a balloon on a string.
Nomophobia - the fear of being without your mobile phone
Octophobia - the fear of the number eight
Plutophobia - the fear of money
Xanthophobia - the fear of the color yellow
Many of us can't imagine these very unusual phobias but to those people who have them they are very real and can cause all types of problems. I've read that there may be more people that have these strange phobias than we know because many people feel too embarrassed to report them.