Health is the combination of two words, HEAL + TH; means which HEALS is Health. In simple words, the body which can heal its all wear, tear and interventions of all unwanted.
Please note that here physical stamina or gymmed-muscle-pack is not defined as health. A physically-strong-prizefighter who may not be good at healing; could not be called as healthy, for sure.
In modern concept, there different dimension of health like; physical, mental, spiritual etc. No doubt, they are interrelated, but the basic of all these factors is physical health to a great extent.
Everything is related to the physical existence of the individual. As one passes away, he leaves the world behind. Therefore, it is utmost important to care for the body. It is said in Vedic literature, “Body is temple.” And health is its deity.
Disease = Dis + ease, not at ease. It is quite simple & self- explanatory term. Start from the first civilization to the modern; the man has been searching/ researching the cause of illness. Theories after theories, disease after diseased and hence, their remedies did change, but not the causes.
One thing is quite clear that all creatures, including human being, are disease free by nature. But, the human beings are the creature that comes in its contact to do get ill. Therefore, the Disease, Doctors, Diagnosis & Drugs do come in picture.
Concluding that point, it could be said that something wrong being done by the man-kind, which causes him to face illness. Knowingly or unknowingly, he invites the diseases.
As said, Human being is healthy by default and gets ill because of his own follies. But, it is obvious that something come in between the health & body, which deprives the body from its wellbeing state. This unknown thing is surly neither the part of the body nor the body wants to retain it anymore. We may call it waste matter, morbid matter, foreign matter or vicar. It is well known as toxin worldwide.
Here I would like to add by widening the meaning of toxin; if a thought comes to the mind, which it turns disturbs the state of wellbeing, should surely be called as toxin. It is mentioned as manovikar in Vedic literature.
Immunity is like the defense system of a country; which scans and takes the appropriate action to safeguard the body from its enemies i.e. the toxin. Everybody is well aware of it.
No clear definition could be derived till date , but to sum up the things to the most, let me tell you, ‘ This is the system, who se essential job is to distinguish self from not-self, to recognize and take appropriate action against any material that ought not to be in the body, including a b normal & damaged components. “For example it can seek out & destroy disease germs and cells infected by germs, as well as recognize & destroy tumor cells. In deciding what belongs to the body and what does not.
There are four routine exit gates, Lungs, Colon, Kidneys and Skin; to repel out the unused waste material from the body. But because of so many reasons it could not get excreted from the body, hence stocks within it and forms in the form of morbid matter, also called 'Toxin'.
As said, Immunity detects and pressurises the toxin to be out of the body by any means. This process, which is like war within body between the Toxin and Immunity to possess the power and reign over the body; is called healing process.