The affix śas comes optionally after crude forms denoting numbers and words denoting units of a coin in the singular number when a distributive sense is to be expressed (and the word is a kāraka).,
Thus द्वौ द्वौ मोदकौ ददाति = द्विशो मोदकौ ददाति \He gives two sweet-meats to each\. So also त्रिशः ॥ Similarly after words in the singular number as, कार्षापणशो ददाति \he gives a Karshapana coin to each\. So also माषशः, पादशः ॥ That by which the sense of unit is expressed is called eka-vachana. The words karshapana &c denote quantity, but their function in the sentence is to denote one-ness i. e. one to each, though in fact many are given.
Why de we say \after Numerals and units of coin\? Observe घटं घटं ददाति \he gives a pot to each\. Why do we say \when a distributive sense is meant\? Observe द्वौ ददाति \He gives two\. कार्षापणम् ददाति \he gives a karshapana\.
This rule of course applies when the word is in relation with a verb viz. when it is a karaka, and not when it is in the genitive case governing another noun. As द्वयोर्द्वयोः स्वामी \Lord of two each\. कार्षापणस्य कार्षापाणस्य स्वामी \Possessor of a karshapanas each\. In fact the work \karakat\ of the last sutra is understood here also. This sutra is exception to 8.1.4.,