The ancient Hindu sages have recognised that the body and the mind form one unit and that this unit is of fundamental importance in achieving anything worthwhile in life. Hence each should be kept in a healthy condition and in harmony with the other. Vyādhi (illness of the body) and ādhi (illness of the mind) are both considered to be serious obstacles in the path of progress, whether temporal or spiritual.
In most general terms, anything that disturbs the equilibrium of the body is a vyādhi and anything that upsets the equi-poise of the mind is an ādhi. The ariṣaḍ-vargas or six enemies viz., lust, anger, greed, delusion, pride and envy, as also worries and anxieties are examples of ādhi. Rāga (attachment) and dveṣa (aversion) are the root causes of all ādhis. Conquest of these will help in removing the ādhis.
In the dharmaśāstras, the word is used in the sense of a pledge, deposit or article of mortgage.