Pathological preoccupation with one subject.
A compulsive preoccupation with one idea or activity.
A state of mental disorder in which a person concentrates attention on one idea.
The state in which a particular delusion or set of delusions is present in an otherwise normally functioning person.
A form of mental illness, in which the affected person has delusion upon one subject, although he or she can converse rationally and is a responsible individual upon other matters.
Mental illness characterized by distortion of thought processes concerning a single subject or idea.