रसायन :

रसायन ( rasāyana )
Meaning: The term Rasayana comprises of two words,I,e Rasa and Ayana, Rasa signifies either Rasa Rakthadi Dhatus(tissues) of the body, Ayana convey the sense of Apyayana, which suggest a measure or methodology to saturate or enrich or conduct a special benefit to the body .Based on these principle, it has been said that one which capacity to enrich the Sapthadhatu of the body or the drugs possessing the qualities to saturate or replenish the Dhatu(tissues). Precisely stated as drug or food which has capacity to prevent ageing, improves longevity, provide immunity against the diseases, promote mental competence, increase vitality and luster of the body.