What is the difference between Illusion and Hallucination?

Illusion

1. Illusion is a kind of wrong  perception.

2. In illusion, an external stimulus is always present. In other words, illusions are caused by external stimulations.

3. Illusion is almost universal.

4. Normal persons suffer from illusions.

5. The same situation arouses the same type of illusion in most people.

Hallucination

1. Hallucination is a false perception.

2. In hallucination, no external stimulus is present. Hallucinations are caused by internal stimulations.

3. Hallucination is a personal experience.

4. Hallucinations are mostly confined to mentally ill persons and to those people under the influence of drugs. The character of hallucination is determined by the individual's present and previous experiences.

5. The same situation may not arouse hallucination in all. There are individual differences with regard to hallucination. The same individual may experience different hallucinations are different occasions also.