Sanskrit for ‘sign’, nimitta is a characteristic mark which acts as a sign to identify the experience of deep concentration on entering a jhanic state of meditation. Descriptions of nimitta can be found in the ancient texts Visuddhimagga and Vimuttimagga. It is thought that without sufficient concentration to produce a nimitta, full meditative absorption is not possible.
Nimitta arises spontaneously during mindfulness breath meditations. By knowing and understanding these signs, both the teacher and student are able to assess the level of concentration that is being attained during the practice. There are three types of nimitta:
Parikamma-nimitta – also known at the preparatory sign, this is the perception of an object at the beginning of concentration
Uggaha-nimitta – also known as the acquired sign, in which the mind reaches a mild degree of concentration with an unsteady or unclear image
Patibhaga-nimitta – also known as the counter-sign, where a clear and static image is a sign of pure concentration.
After working through the three types of nimitta, pure concentration leads to full jhanic absorption