Though this word means a problem or a difficulty that produces sorrow and suffering, the Yogasūtras of Patañjali (200 B. C.) uses this word as a technical term (vide 2.3; 1.24). Traced from the root-verb ‘kliś’ it means anything that causes sorrow, suffering and bondage.
The kleśas are five in number. They are: avidyā (nescience), asmitā (ego-sense), rāga (attachment), dveṣa (hatred, aversion) and abhiniveśa (excessive attachment to life, fear of death).
They can be eliminated by meditation on the ātman (the Self) and ultimately by the dissolution of the citta or the mind, in its cause, the pradhāna (insentient material cause of the whole creation).