येन तस्य विशेषः कथ्यते, तद्विशेषणम् ।
yena tasya viśeṣaḥ kathyate, tad viśeṣaṇam |
(Hari-nāmāmṛta-vyākaraṇa: 305)
“That by which its [i.e., a viśeṣya’s] distinguishing feature (viśeṣa) is described is [called] a viśeṣaṇa (modifier).”
Commentary
According to context, a viśeṣaṇa may be an adjective, adverb, noun in apposition, or a predicate.