Umāsvāti defined the definition of satf but did not define the definition of utpāda, vyaya etc. But later ācāryas pondered upon the definition of utpāda. Ācārya Akalaṁka (8 cent. CE), the commentator of Tattvārtha Rājvārtika quotes svajātyaparityāgena bhāvāntarāvāptirutpādaḥ.[1] It means utpāda is nothing but a modification of a substance without giving up its own nature. With a slight difference, Ācārya Pūjyapāda Devanandī (9th cent. CE) defines utpāda or origination as:
cetanasyācetanasya vā dravyasya svāṁ jātimajahat ubhayanimittavaśād bhāvāntrāvāptirutpādanamutpādaḥ mṛtpindasya ghataparyāyavat.[2]
It means, the attainment of other modes by souls or other substances, by means of external and internal causes, without giving up their essential characteristics is called as utpāda. For instance, the production of a pitcher from clay.