Social anxiety disorder is a word commonly used to describe the experience of severe anxiety (great emotional discomfort, severe shyness, fear, or worry) in social situations, talking  with others and being criticized or scrutinized by other people. It happens early as an infant as a normal part of the development of social functioning, but may go unnoticed until teen years . People vary in how often they experience social anxiety or in which kinds of situations. It can be related to shyness or other emotional or temperamental factors, but its exact nature is still the subject of research and theory.

A psycho pathological form of social anxiety is called social phobia or social anxiety disorder. This disorder can result in a reduced quality of life for those having it. Social anxiety can be self-integrated and persistent for people who suffer from Obsessive compulsive disorder (OCD), which can make the social anxiety even harder to control, especially if ignored.
Some use the terms "social anxiety" and "social phobia" interchangeably.

Social anxiety as a disorder
Extreme, persistent and disabling social anxiety may be diagnosed as social anxiety disorder. The experience is commonly described as having physiological components ( sweating, blushing), cognitive/perceptual components (e.g. belief that one may be judged negatively; looking for signs of disapproval) and behavioral components e.g. avoiding a situation (Avoidant personality disorder).

The essence of social anxiety has been said to be an obsessive expectation of negative evaluation by others. One theory is that social anxiety occurs when there is motivation to make a desired impression along with doubt about having the ability to do so. Although the "official" clinical name for the disorder, as listed in the DSM and ICD, is Social Phobia or Social Anxiety Disorder, support groups for people who have the disorder often refer to it as simply social anxiety.

Clinicians and researchers continue to struggle with definitional problems regarding the constructs of shyness, social anxiety and social phobia (social anxiety disorder). Each shares similarities, yet each has been used to define distinct aspects of psychological life as it relates to interpersonal functioning.