na vā caturlakṣaṇo yasmāt kvacid ekalakṣaṇo dvilakṣaṇastrilakṣaṇo 'pi vā nyāyyaḥ, yasmād anyathānupapattir ekaṃ lakṣaṇaṃ tenaikalakṣaṇa iti vyapadiśyate
Or it may not be four-featured, since in some cases [a probans] with one, two, or three features is [also] valid, [and] since being otherwise impossible is [its] one characteristic, therefore it is called one-featured.