This document summarizes personality disorders by discussing their definition, clusters, and specific disorders. Personality disorders are categorized into three clusters - A, B, and C - based on their characteristics. Cluster A disorders include paranoid, schizoid, and schizotypal personalities. Cluster B disorders are dramatic/erratic and include antisocial, borderline, histrionic, and narcissistic personalities. Cluster C disorders are anxious/fearful and consist of avoidant, dependent, and obsessive-compulsive personalities. Each disorder is then defined in 1-2 sentences. Treatment may include therapy and medication, depending on the specific disorder.