What does Dosha actually mean?
The universe consists of five elements - Ether, Air, Earth, Fire and Water- and the human body is composed of a combination of them. Furthermore, three principle bio-energies known as the doshas(Vata, Pitta and Kapha) exist in all matter and are composed of different combinations of the five elements. The Sanskrit word dosha translates to “that which can cause problems/disturbance”, where there is imbalance, there is illness or disease.
Imbalance occurs because one or more of the energies or elements gets increased quantitatively or altered qualitatively. There is no experience, whether a thought, an emotion, the climate, food, lifestyle, etc. that does not have at least one of the twenty qualities (gunas) which, by its action, yields an effect in the physiology.
Although the concept of the doshas is unique to Ayurveda, it is not unlike the traditional Western idea of three basic body types- ectomorph (lean and delicate), mesomorph (compact and muscular) and endomorph (stocky). Prakriti(genotype) is your constitution you are born into, Vikrati(Phenotype) is the dosha influenced by environment etc. (epigenetics). A person has a permanent or stable nature for the entire life and efforts to maintain or change physiology must keep this balance point in mind.
In addition, each type will suggest an area tending to go out of balance, a disease tendency, requiring lifelong attention to maintain balance. A Vata type naturally tends to constipation, arthritis, anxiety; a Pitta type tends towards inflammations, infections, ulcers; and Kapha types tend to overweight, diabetes, congestive disorders, etc. Prakriti helps to explain why people react differently to the same things. The medical implication for this is that certain people/animals will have a natural predisposition or sensitivity to certain medicines, and this can be predicted.