An inference when based on a middle term that is only positively related to the major term and the knowledge of Vyapti between the middle and major terms is arrived at only through the agreement in presence is known as Kevalanvayi.Vyapti means a correlation between two factors, that is one pervaded (vyapta) and the other that pervades(vyapika).Anumana or inference is a rational process in which on the basis of knowledge of an object a certain knowledge of other objects is received.Classification of inference or Anumana on the basis of vyapti is of three kinds;Kevalanvayi AnumanaKevalavyatireki anumanaAnvayavyatireki AnumanaKevalanvayi Anumana occurs when the middle term is always positively related to the major term.The two terms agree only in the presence and there are no negative instances of their argument in the absence.For example;All men are mortalRam is a manTherefore, Ram is mortalHence An inference when based on a middle term that is only positively related to the major term and the knowledge of Vyapti between the middle and major terms is arrived at only through the agreement in presence is known as Keval\(\overline{a}\)nvayi.Additional InformationA Kevala-Vyatireki Anumana inference is that in which the middle term is negatively related to the major term.?Anvaya vyatireki occurs when the middle term is both positively and negatively related to the major term. In other words,it is called the Double agreement.Sheshvat anumana is an inference in which we infer the unperceived cause from a perceived effect. For e.g. we infer the past rain from a swift muddy current of water in the river.