Ayurveda is a word formed by two terms: ayushmeaning life and vedawhich means science or knowledge, Ayurveda literally means science or knowledge of life. Commonly its think that Ayurveda is the system of traditional medicine in India, this is certainly true, but is only part of the truth.
In CharakaSamhitaa definition of Ayurveda is given: Ayurveda is the science of useful life and un useful life (hitayu, ahitayu), happy life and unhappy life (sukhayudukhayu), the science that explains the value, quality and extent of life (mana) and is the knowledge Supreme Soul or Supreme Consciousness (tat) .Later in the text is the definition of life (ayush), which is described as the combination of body, mind and soul:
The term ayusrepresents the combination of body, sense organs, mind and soul2 . The mind, the self (soul) and body, the whole is like a tripod, the world is supported by their combination, they constitute the substrate on which rests the living world.

HETU: The reasons of health and the causes of the disease (etiology)
LINGA: Signs of health and symptoms of the disease (symptoms)
AUSADHA: Treatments to protect the health and remedies to cure the disease

The pathogens in the body are vata, pitta and kapha, while doshasofthe mind are rajas and tamas. One of the most important concepts of Ayurvedais to dosha.
In the body doshas are called vata, pitta and kapha.

• Vata is air (vayu)
• Pitta represents fire (agni)
•  Kaphais water (jala)

If you keep the balance of three doshas, the whole system remains inbalance, all bodily functions work normally maintaining the health of the body.

All three components bodily vata, pitta and kapha, when they are in theirnatural state, contributing to the functioning of the sensory faculties to createstrong, healthy appearance, happiness and long life in living things. As virtue,wealth and satisfaction of desires, these body parts, if properly directed, bringimmense happiness to living beings in this life and in the future. If on the otherhand, these components are unbalanced, like a mismatch in the seasons, causingundesirable effects and disastrous consequences in the lives of living beings in the world.

Besides the three bodily doshas, there are two mental doshascalled rajasand tamas, the quality of motion and inertia, which together with the luminousquality (sattva) are the three qualities (gunas) of the mind. Since sattvathe
quality of purity and light has no pathogenic effects on the mind. When youfree from rajas and tamasthe human being obtains bliss and freedom fromlimitations due to the predominance of sattva8 . Instead rajas and tamas, producing excitement and inertia, attachment and aversion, preventing themind to have a balanced view of the reality of things, so they are consideredmental doshas.

There is an indissoluble union between mental doshas rajas and tamas.Tamascan not express its action without rajas9 . The state of mind affects thebody’s equilibrium since there is a direct relationship between the qualities of
mind and physical doshas:

• Rajas influence vata
• Sattvainfluence pitta
• Tamasinfluence kapha.

Prakritiand swabhavahas synonymouslyindicate the individual nature of living beings. Everyone is born with some physical and mental characteristics that remain throughout life, these features are part of prakritior individual Personality.

Source of Prakriti

According to SushrutaSamhita, there are seven types of prakritidetermined by the dominance of a single dosha, the combination of two doshasand the combination of all three doshas.The seven types of prakriti are:

• Vata
•  Pitta
• Kapha
• Vata-Pitta
• Pitta-kapha
• Vata-Kapha
• Vata-Pitta-Kapha

The predominant doshasat the time of the union of sperm (shukra) and egg (shonita) determine the constitution. It means that personality primarily genetic in origin. Egg and sperm carry within them the formation of both parents. According to CharakaSamhita, there are four factors that determine the prakritiof the fetus:

• State of doshasin the sperm and egg at time of conception (shukrashonitaprakriti)
• Predominance of doshasduring pregnancy and conditions of theuterus during gestation (kalagarbhasayaprakriti)
• Diet and lifestyle of the mother during pregnancy (aturaharaviharaprakriti)
• Predominance of the elements during gestation (mahabhutasvikaraprakriti).

For example, if dominated by fire and water (jala and agni) the fetus will have a dominant with pitta prakriti, prakritias the human beings is determined from the first moments of life of the fetus.

Besides the four factors above, Charakadescribes other factors that determine the constitution of the individual:

•  Genetic factors
• Family characteristics
• Birthplace
• Time, season
• Age of parents
• Individual Characteristics.

For each entity there is a structural body channel (srota) that allows maintenance, growth or decay of that structure. The srotaare channels of movement which is transporting tissues (dhatu) in the form of the substances contained therein, and continually turn from the tissue prior to the next.Theknowledge of channel body is very important for their role in the transport of nutrients to tissues, but also for the transport of toxins to be excreted and eliminated from the body.

When srotametabolic wastes are cleared by the (ama) created by the metabolic processes occurring inside the body, leaving their waste storage sites and move toward the center of the body in the abdominal cavity where it is removed along with the excreta. Channels, veins, arteries, lymphatics, capillaries, ducts, passages, streets, spaces, cavities, mansions, these are the names given to areas visible and invisible in the body. Alteration of channels leads to the alteration of tissue elements that reside in them or are transported through them, a stream in improper srotacreates disease. Alteration of channels and components of body tissues affect the channels and tissues that are connected with them. Because of their  pathogenic nature doshasvata, pitta and kaphaare responsible for the alteration
of channels and tissues.

There are Four Types of Alteration in the Flow of Substances Carried in Srota:

• Excessive flow
• Obstruction
• Nodule formation (hypertrophic growth in the channel)
• Improper flow of substances into the canal or in the oppositedirection.3

The Channels are of Two Types:

• Those that originate from an internal space inside the body (Interiorsrota)
• Those outside the mouth is in contact with the space outside thebody (Exterior Srota).

The Interiors are Countless Srotabut According to the CharakaInterior Srota:

• Pranavahasrota, carries the breath of life
• Udakaor jalavahasrota, carrying water
• Anna vahasrota, carrying food
•  Rasvahasrotacarrying the plasma
• Raktavahasrota, carrying blood
• Mamsavahasrota. carries the muscle tissue
• Medavahasrota, carries fat
• Asthivahasrota, carrying the bone
• Majjavahasrota, carrying the bone marrow
• Shukravahasrota, carrying the reproductive tissue
• Mutravahasrota, carries urine
• Purishavahasrota, carries feces
• Swedavahasrota, transports sweat.
• ArtavaVahaSrotaCarries the Menstrual Flow
• StanyaVahaSrotaTube that Carries Milk
• Mano VahaSrotaCarries the Thought

Sushrutaalso describes nine srotaoutside the body that communicate with the space outside it:
Exteriors Srota

• 2Ears
• 2Nostrils
• 2Eye
• 1Mouth
• 1Anus
• 1Urinary tract.