Grahita, Grahana and Grahya are terms in Samkhya and Yoga. Here is a look at the meaning of these words. Sage Patanjali has mentioned these words in Yoga Sutra in connection with the definition of deep mental absorption called samapatti (I: 41).
These three are the main categories into which the 25 tattvas forming the universe according to Samkhya and Yoga can be grouped.
Grahita is the soul, called drashta in Yoga. It is the seer, perceiver of the universe.
Grahana means a sense organ. There are in all 13 sense organs, out of which ten are bahya (external) and three abhyantara (internal), also called antah-karana. Karana, which is same as grahana, is the means or instrument of knowledge. The internal organs are buddhi (intellect), asmita or ahankara (the ego feeling), and manas (the mind). The ten external organs are divided into two groups namely, gyanendriya (sense organs) and karmendriya (motor organs).
Grahya means that which is known or received in knowledge, i.e. the object of knowledge. They are ten in number, including five mahabhutas (gross objects) and five tanmatras (subtle objects).
Thus in all 24 basic principles form the grahana, grahita and grahya.
The 25 tattva (basic principle), namely prakriti (the primordial nature), is not included in this classification of the three categories. It is neither a grahya, nor a grahita and not even a grahana. It is the mother, the original source of the 24 tattvas.
Samapatti is defined by Sage Patanjali as a state in which the citta (mind) is stabilized upon and unites itself totally and completely with any one of the 24 tattvas, grouped in the three categories of grahita, grahana and grahya, as mentioned above.
A History Of Indian Philosophy (2004) Surendra Nath Dasgupta, Motilal Banarsidass, New Delhi.
Encyclopedia of Hinduism Volume IV page 351 - 52 - IHRF