An example of a "negative symptom" of schizophrenia is

Schizophrenia is a mental disorder in which a person's ability to think, interpret reality changes. Schizophrenia can be characterized by hallucinogen, loss of emotions, delusion, disorder thoughts and poor motivation.

Negative symptoms characterized by the functional disability or reduced ability to function properly in schizophrenia patients, for example, the person is not concerned about personal hygiene or the person is emotionless( does not change expressions, do not make eye contact, etc).  

Symptoms in male starts during early to mid-20s and in female, it appear in late 20s. This disorder is uncommon in children.