The affix śyan is optionally used after the verb yas 'to strive' when it is used without a preposition and when a sārvadhātuka affix denoting an agent, follows. ,
Thus यास्यति or यसति 'he strives'. But no option is allowed in आयस्यति, प्रयस्यति. The root यस् belongs to the Divadi class.,