An anxiety disorder is a psychological disorder characterized by overwhelming apprehension of fear (anxiety) to the point where it becomes disabling and affects sufferers' daily lives.

Stress and anxiety are normal in life, so if someone experiences these things occasionally, it's not thought to be a disorder. 

Common types of anxiety disorders include:
- generalized anxiety disorder (GAD)
- phobias (ex. social phobia, agoraphobia, etc.)
- panic disorder
- obsessive-compulsive disorder (OCD)*

*OCD isn't officially categorized as an anxiety disorder in the Diagnostic and Statistical Manual for Mental Disorders Fifth Edition (DSM-5), but it could be considered one due to the anxiety from obsessions and/or compulsions.