The traditional system of medicine widely practiced in Tamil Nadu is:

Siddha
Ayurveda
Unani
Homeopathy

The correct answer is Siddha.

Siddha is a traditional system of medicine that originated in India. It is one of the oldest systems of medicine in the world, and is still widely practiced in India today. Siddha is based on the belief that the body is made up of five elements: earth, water, fire, air, and ether. These elements are in a constant state of flux, and when they are out of balance, it can lead to illness. Siddha aims to restore balance to the body by using a variety of methods, including herbal medicine, diet, and massage.

Ayurveda is another traditional system of medicine that originated in India. It is based on the belief that the body is made up of three doshas: vata, pitta, and kapha. These doshas are in a constant state of flux, and when they are out of balance, it can lead to illness. Ayurveda aims to restore balance to the body by using a variety of methods, including herbal medicine, diet, and lifestyle changes.

Unani is a traditional system of medicine that originated in the Middle East. It is based on the belief that the body is made up of four humors: blood, phlegm, black bile, and yellow bile. These humors are in a constant state of flux, and when they are out of balance, it can lead to illness. Unani aims to restore balance to the body by using a variety of methods, including herbal medicine, diet, and lifestyle changes.

Homeopathy is a system of medicine that was developed in Germany in the 18th century. It is based on the belief that “like cures like.” This means that a substance that can cause symptoms in a healthy person can be used to treat those same symptoms in a sick person. Homeopathic remedies are made from very dilute substances, and are often taken in the form of pills or drops.

Siddha is the traditional system of medicine widely practiced in Tamil Nadu. It is a holistic system of medicine that aims to treat the whole person, not just the symptoms of the illness. Siddha uses a variety of methods to treat illness, including herbal medicine, diet, massage, and yoga.