What is the difference between Social Anxiety, Selective Mutism & Avoidant Personality?

Social anxiety is an anxiety disorder based on performance dynamics. Selective mutism is an example of social phobia as the anxiety has morphed into avoidance. Avoidance due to anxiety is a phobia. Selective mutism is also a manifestation of obsessive compulsive disorder. The more the anxiety creates avoidant behavior, the more potential there is for the avoidance to become ingrained in the personality. One of the ways that the severity of the problem can be measured is by the degree of avoidance. Therefore; avoidant personality applies to both social anxiety and selective mutism.