CBSE Class 9 Answered

Immediate cause is the cause which immediately kindles a disease into action, when there exists a predisposition towards it. These are usually the infectious, physiologic or anatomic changes leading to sickness. Eg - Coronavirus causing SARS or hypocalcemia leading to seizures

A contributory cause is a condition whose presence makes it more probable that a particular disorder will occur, but that cause is neither necessary nor sufficient for the occurence of the disease. eg. - A history of smoking cigarretes is neither necessary nor sufficient for an individual to develop lung cancer, since most smokers do not develop lung cancer. Also several people with lung cancer do not show any history of smoking. So smoking increases the risk of getting lung cancer, but is not required.