Of sup (which is a pratyāhāra formed of su the first of the case affixes and the final p of the last of them), the expressions in each successive set of the three, are also severally called singular, dual and plural.,
The sup or the case-affixes by which nouns are declined are 21 in number corresponding to the seven cases, see sutra 4.1.2. They also have three numbers singular, dual and plural.,