In Freudian psychoanalytic theory,<unk> s are psychological strategies brought into play by individuals, groups, and even nations to cope with reality and to maintain self-image. Healthy persons normally use different<unk> s throughout life. An ego<unk>  becomes pathological only when its persistent use leads to maladaptive behavior such that the physical and/or mental health of the individual is adversely affected. The purpose of the Ego<unk> s is to protect the mind/self/ego from anxiety, social sanctions or to provide a refuge from a situation with which one cannot currently cope.
They are more accurately referred to as ego<unk> s, and can thus be categorized as occurring when the id impulses are in conflict with each other, when the id impulses conflict with super-ego values and beliefs, and when an external threat is posed to the ego.
The term<unk> " is often thought to refer to a definitive singular term for personality traits which arise due to loss or traumatic experiences, but more accurately refers to several types of reactions which were identified during and after daughter Anna Freud's time.
Defence mechanism
Emotional contagion
Complication 
Penetrance
Attachment 
Exaptation
Limiting factor
Disequilibrium causes