The word ayurveda has been coined by the conjunction of two Sanskrit words, "ayur" meaning life and "Veda" meaning knowledge. The word together means the knowledge of life. In ayurveda the process of ayur (life) is considered as a combined state of body (sharira), senses (indriya), psyche (mana) and soul (atma). Among these the visible body is made of panchamahabhoota and is called sthoola sharir whereas the sense, psyche and soul are invisible and thus are called sukshma sharir or linga sharir. Ayurveda not only consists of natural scientific methodology of medication but also provides the way of life.

During the course of time Ayurveda, the way of life and its knowledge became the science of life, which has its root in ancient Vedic literature and encompasses our entire life, the body, mind and spirit.

Punarjanma
It is believed that death takes away the sukshma sharir to the heavenly abode leaving behind the sthoola sharir that decomposes back to its constituent elements, the panchamahabhoota. The sukshma sharir takes rebirth (punarjanma) until it attains moksha.

The splitting of the sukshma sharir into indriya, mana and atma after it attains salvation (moksha) follows this life and death cycle. Indriya and mana that originate from the nature, surroundings (prakruti) remerge with the same whereas atma, the image of parmatama merges back into it.

The other instance that is believed in, is the non- attainment of salvation (moksha) after death. This leads to the combining of the sukshma sharir i.e. the indriya, mana and atma with the new sthoola sharir at the time of shukra shonita sanyoga (fertilization) in the uterus.

This combination of sukshma and sthoola sharir occurs in accordance with the karmafala that is to be enjoyed by the new sthoola sharir. The karma (deeds) of the previous sthoola sharir decide the karmafala of the new sthoola sharir.

It doesn't always happen that the sukshma sharir combines with species of sthoola sharir same as itself. According to vedic science the sukshma sharir can combine with any of the species among the 8.4 million species that exists.

Attainment of moksha is one of the chaturvidh purushartha. (four main objectives of life) and the process of splitting and combining of the sukshma sharir with the sthoola sharir continues till moksha is attained.

Atma is comparable to god, the creator and is believed to be the almighty. Once the sukshma sharir and the sthoola sharir have atma attached to it, due to karmafalbandhan all its strength and might is lost and he has to lead this cyclical phase of life according to the karmafala.

In ayurveda itself the Sanskrit word ayur has synonyms that possess the same meaning and value as life itself. Few synonyms are:

Dhari

As the physical properties of the body is sustained (dharna) during life.

Jeevita

As the lively activities are carried out.

Nityaga

As the time of life is continuously spent.

Anubandha

As life is possible with the combination (bandhan) of the sukshma and the sthoola sharir.

Charak Sootra 1/41

In ayurveda ayu (life) can be classified as:

• Sukha Ayu: The ayu that leads a healthy life. Person has good health.
  
• Dukkha Ayu: The ayu that live a diseased life. The person suffers with some disease all his life.
  
• Hita Ayu: The ayu that lives life by serving the society.
  
• Ahita Ayu: The ayu that live life in destructive activities.

Ayurveda is the science of life that not only deals with Sukha Ayu, Dukkha Ayu, Hita Ayu, Ahita Ayu but also deals with the ways and means to achieve health the path that leads to disease.

In all ayurveda deals with quantum of the Ayu, the life.