Viparyayoh mithyaa gyaanam atadroop pratishtham
Translation: Patanjali details viparyay as the second modification of the mind. Viparyay translates as opposite or alternate cognition, that is to take something to be something else. It is the false gyan of the subject, something which does not establish its true/actual form. For example, there is a rope lying in front of you and you scream 'snake'. You get the faulty experience of a snake while looking at a rope. 'Snake' is an alternate, faulty cognition (viparyay) of the actual form of the object which is a rope.