What is the definition or description of: phobia?

Unnecessary fear: An irrational fear of a specific object, activity, or situation that leads to a strong desire to avoid it. Such fears can be considered anxiety disorders or symptoms characterized by unnecessary avoidance of a situation out of fear. Avoidance is the hallmark of a phobia. And, avoidance serves as a sort of fuel for the phobia.

Phobia: It comes from the greek word phobos, meaning fear. Is a type of anxiety where there is persistent fear of an object or situation, resulting in marked distress or interference with social activities & performance, leading to avoidance.