Final answer:
A phobia is an extreme, irrational fear of a particular object, situation, or activity that causes significant distress and can lead to avoidance behaviors. An example of a phobia is arachnophobia, the fear of spiders.
Step-by-step explanation:
A phobia is an intense, irrational fear of a specific object, situation, or activity. The fear is disproportionate to any actual danger presented and can cause a significant amount of distress, even leading to the avoidance of everyday situations. A famous case study of a phobia is the one analyzed by Sigmund Freud, which he titled Analysis of a phobia in a five-year-old boy. In this study, he explored the phobia of a young boy known as 'Little Hans' who had an irrational fear of horses. One common type of phobia is arachnophobia, which is the fear of spiders.