Ostracism is being deliberately left out of a group or social setting by exclusion and rejection. Groups and individuals alike can ostracize others and be ostracized themselves. Although social rejection is an inevitable part of human existence, prolonged or unreasonable ostracism can lead to loneliness, depression, and/or aggression. An example of ostracism is a student deliberately not inviting a particular person to their party although they invited everyone else in their class.