The affix tumun is added to every verb when another verb having the sense of 1. śak 'to be able' 2. dhṛṣ 'to make bold' 3. jñā 'to know' 4. glai 'to be weary' 5. ghaṭ 'to strive' 6. rabh 'to begin' 7. labh 'to get' 8. kram 'to set about' 9. sah 'to bear' 10. arh 'to be pleased or to condescend' 11. as 'to be'.,
The use of the Infinitive in तुमुन् formed by this rule, differs from that given in sutra 3.3.10. In that sutra the Infinitive had the force of 'purpose' and here there is no such force. Moreover in this case there is an upapada in construction, though that upapada is a verb; in rule 3.3.10, there was no such upapada.
Thus शक्नोमि भोक्तुम् 'I am able to eat'. Similarly जानाति—ग्लायति—घटते—आरभते—लभते—प्रक्रमते—सहते—अर्हति—अस्ति—भवति—or विद्यते भोक्तुम् 'he knows', he is wearied, he strives, he begins, he gets, he proceeds, he bears, he condescends or he is, to eat'.
This sutra presents a knotty point. Bhattoji Dikshita says अर्थग्रहणमस्तिनैव सम्बध्यते अनन्तरत्वात् i.e. the sutra gives roots from शक् to अर्ह and roots having the same sense as अस् 'to be'. But this is hardly consistent with the almost overwhelming evidence of usage. According to Dikshita's interpretation, पारय 'to be able' cannot be used with the Infinitive, but न पारयामि निवेदयितुम् (S. 4), पारयिष्यस्यत्रभवत्यअपरान्दधुम् (M. 3.) are instances from a standard author; similarly विद् 'to know' cannot be used with the Infinitive; but न च वेद सम्यग् द्रष्टुम् न सा (R. VI. 30) is as good an instance. We must, therefore, suppose that the sutra indicates the existence of an interpretation connecting अर्थ with all the preceding roots; otherwise we shall have to condemn as wrong, all such constructions as those given above. Taking this view I have interpreted the sutra, connecting अर्थ with all the above roots.- Apte's Composition.,