This paper examines the Sa skya pa’s view of different definitions of sapakṣa (“similar set”) given by Dignāga. Sa pan. and his followers, such as ’U yug pa and Shākya mchog ldan, only accept the definition of sapakṣa that is given in the Pramaāṇasamuccaya, and assert that sapakṣa is a set of objects that are similar to the subject on account of possessing the property to be established either in actuality or conceptually. However, according to Rong ston, sapakṣa that occurs in improper arguments is to be distinguished from one that occurs in proper arguments, since sapakṣa that occurs in improper arguments need not be similar to the subject, but rather it is a set of objects that have the property to be established. Therefore, this implies that another definition of sapakṣa, namely, “a set of objects that is similar to the property to be established,” given in the Nyāyamukha is also justifiable in the case of improper arguments such as “Sound is permanent because it is an object of cognition.” Nevertheless, he makes a slight modification to this definition in the following manner: A set of objects that have the property to be established.