How is schizoaffective disorder different from schizophrenia?

Mood symptoms. Both disorders have prominent distortions of reality, with hallucination, delusions, and problems with thought processes. However, schizoaffective disorder also has prominent mood symptoms, depresison or mania, that occur in the same timeframe. Schizophrenia can have some associated mood disturbance, but usually not during the episode.
They're similar. Officially, schizophrenia is a thought disorder characterized by psychosis which consists of hallucinations and/or delusions. Schizoaffective disorder is when a person fulfills diagnostic criteria for a mood disorder plus has periods of psychosis during times when the mood disorder symptoms are not present. There are two types of schizoaffective, bipolar & depressed types.

Related Questions

What symptoms are different in schizophrenia and schizoaffective disorder? Is one a disease of the brain, other disorder?

Both brain disease. Both of these illnesses are "brain diseases, " and both have psychotic symptoms such as delusions, paranoia, hallucinations, thought disorder, etc. Schizoaffective patients also have mood dysregulation, but pure schizophrenics don't. Treatment for schizophrenia may be antipsychotics alone; schizoaffective people also need mood stabilizing agents. They may deal with mania & depression, + psychosis.

Is schizoaffective disorder a condition in it's own right? Or is it basically two different illnesses in the one patient (schizophrenia and bipolar)?

Considered one. It is currently considered one disorder. I find the diagnosis to be used as somewhat of a 'catchall' category professionally. I usually try to refine this diagnosis in my work with people.

Is schizoaffective disorder schizophrenia?

No. Schizoaffective disorder is similar to schizophrenia. In schizoaffective disorder, though, there are also times when there is mania and/or depression along with the hallucinations or delusions.
No. By definition, there is a difference. Schizophrenia is characterized by psychosis which is when a person experiences hallucinations and/or delusions. A mood component is not part of such a clinical picture. Schizoaffective d/o is when a person has a major mood disorder and has also had periods of psychosis during times when they had no disturbance of their mood. There's bipolar & depressed types.
Schizoaffective. Schizoaffective disorder is an extremely serious illness that can be thought of as a combination of schizophrenia (psychosis) and bipolar disorder (the old term being manic depression) with involves extreme mood swings.

What is the difference between having schizophrenia and schizoaffective disorder?

Certain Similarities. Schizophrenia is a severe brain disorders in which people interpret reality abnormally. Schizophrenia may result in some combination of hallucinations, delusions, and disordered thinking and behavior. Schizoaffective disorder includes the symptoms of schizophrenia and includes mood disorder symptoms such as depression or mania.
They're similar. Officially, schizophrenia is a thought disorder characterized by psychosis which consists of hallucinations and/or delusions. Schizoaffective disorder is when a person fulfills diagnostic criteria for a mood disorder plus has periods of psychosis during times when the mood disorder symptoms are not present. There are two types of schizoaffective, bipolar & depressed types.
Schizoaffective. Schizoaffective disorder is an extremely serious illness that can be thought of as a combination of schizophrenic (psychosis) and bipolar disorder (the old term being manic depression) with involves extreme mood swings. Schizophrenia is about psychosis, but without mood swings.

What's the difference between schizoaffective disorder and full-blown schizophrenia?

Schizo. Schizophrenia is thought disorder, schizoaffective is both disorganized thoughts with affective component not meeting criteria of bipolar disorder.
Both illnesses. Are "full blown" illnesses! In schizophrenia, psychotic symptoms a predominate. In schizoaffective disorder, both mood and psychotic symptom predominate.

How likely it is for homicide to occur during an "episode" when someone has schizoaffective disorder/schizophrenia?

Not likely. The vast majority of people with schizophrenia are not violent and never harm anyone. They are more likely to be victimized than vice versa. They are at high risk for suicide (~20% make an attempt), not homicide. At least one study found that severe mental illness is not an independent predictor of violence. The small fraction of people with schizophrenia who become violent make the headlines.
Very low. Risk of any form of violence is 10% in individuals who suffer from schizophrenia. For reference, risk of any form of violence in those with substance use disorders is 25%.

I was wondering what do people with schizoaffective disorder major in schizophrenia lack in their body?

Nothing lacking. The genetic component - which does indeed seem to play a very big role - has not to my knowledge represent a lack of a chemical or particular transmitter. I'm not sure if you were thinking of replacement/supplement treatment possibilities, but I've never heard of any thing like that. Sorry if this disappoints.

How successful is Abilify (aripiprazole) in managing schizophrenia / schizoaffective disorder with jealousy type delusions?

Good. Abilify (aripiprazole) is an excellent medication. However, as good as any medication is it must be matched with a persons medical condition, diagnosis, and symptoms. This is a discussion which you should have with your doctor who knows these things about you.