Rule. The affix yak comes after a root when a sārvadhātuka affix follows that denotes bhāva or karma. Only ya is heard; the k is a marker. Bhaṭṭoji's gloss: "let the affix yak come after a dhātu when there follows a sārvadhātuka denoting bhāva or karma".
"After a dhātu" (dhātoḥ) is carried forward from SK 2629. "Denoting bhāva or karma" is carried forward from SK 2758, two sūtras later. Bhaṭṭoji's commentators both give these.
Example.
bhū + laṭ, in bhāva (SK 2152; bhū takes no object)
→ the ātmanepada by SK 2679; third person singular → bhū + ta
→ the ta becomes te (SK 2233) → bhū + te
→ te is a sārvadhātuka denoting bhāva, so this rule adds yak → bhū + ya + te
→ yak is marked with k, and such an affix blocks guṇa (chapter 44) → bhūyate.
The agent is not expressed by the ending (anabhihita), so it takes the third case: tvayā mayā 'nyaiś ca bhūyate.
In liṭ there is no sārvadhātuka, so there is no yak: babhūve.
Applies when / blocked by. What is bhāva? Bhaṭṭoji: bhāva is bhāvanā, "bringing about" (utpādanā), that is, action (kriyā). Every root already denotes action, just by being a root. So a lakāra in the sense of bhāva only restates (anūdyate) what the root has said. One of Bhaṭṭoji's commentators compares the dual ending in dvau "two", which restates the twoness the word already names.
Why only the third person? Bhaṭṭoji: there is no co-reference (sāmānādhikaraṇya) with yuṣmad "you" or asmad "I". One of his commentators explains. A lakāra can share its referent with a word only when it denotes the agent or the karma, never bhāva. The third person still comes by SK 2165, śeṣe prathamaḥ: it is the person used wherever the second and first do not apply.
Why only the singular? Bhaṭṭoji: the action denoted by a verb-ending is not a substance (asattva). So two or many of it are not understood. The singular is used because it is the general ending (autsargika). It does not depend on the number one. One of Bhaṭṭoji's commentators contrasts the action denoted by a kṛt affix, which is like a substance: pākau, pākāḥ "two cookings, many cookings". Whether "only the singular" holds without exception, scholars discuss this.
Watch out. Yak comes only before a sārvadhātuka: the endings of laṭ, loṭ, laṅ and vidhiliṅ. The other lakāras take no yak. Liṭ is formed as usual: babhūve. Before sya, sic, sīyuṭ and tās, SK 2757 optionally applies. In the luṅ before ta, SK 2758 brings ciṇ.
[Now the lakāras laṭ and the rest in bhāva ('the action itself') and in karma. By 'bhāvakarmaṇoḥ' (SK 2679), the taṅ [endings come].] Let the affix (pratyaya) yak come after a dhātu [— 'dhātoḥ' carried forward (anuvṛtti) from SK 2629] when there follows a sārvadhātuka denoting bhāva or karma [— carried forward (anuvṛtti) from SK 2758]. bhāva [here] is bhāvanā, '[the act of] bringing about' (utpādanā), [that is,] action (kriyā). And that [action], being what all dhātus denote by virtue of their being dhātus (dhātutvena), is [merely] restated (anūdyate) by a lakāra that has bhāva as its meaning. Because there is no co-reference (sāmānādhikaraṇya) with yuṣmad and asmad, [only] the third person (prathamapuruṣa) [is used]. Because the bhāvanā denoted by the tiṅ has the nature of a non-substance (asattvarūpa), duality and the rest are not understood [in it]; [hence] there is no dual and so on — only the singular. For that [singular], being the general one (autsargika), does not depend on number. The agent (kartṛ), not being expressed [by the tiṅ] (anabhihita), takes the third case (tṛtīyā): tvayā mayā 'nyaiś ca bhūyate ('there is being [i.e. becoming] by you, by me and by others'). [liṭ:] babhūve.
- textual The bracketed opening sentence is missing from our source. NSP p. 463 (scan 0473) prints, in kaumudī type under the heading 'tiṅante bhāvakarmaprakriyā 60' and before the sūtra: 'atha bhāvakarmaṇor laḍādayaḥ | bhāvakarmaṇoḥ 2679 iti taṅ |'. Supplied in square brackets; mūla gap for the Print Check.
- textual Our source reads 'samānādhikaraṇyābhāvāt'; NSP p. 463 (scan 0473) reads 'sāmānādhikaraṇyābhāvāt', as does the TB pratīka 'sāmānādhikaraṇyābhāvād iti' (NSP p. 464, scan 0474). Translated as sāmānādhikaraṇya.
- commentary BM: 'dhātoḥ' comes by anuvṛtti from 'dhātor ekācaḥ' (SK 2629), and 'bhāvakarmavācini' from 'ciṇ bhāvakarmaṇoḥ' (SK 2758). Followed in sutra_en and k1.
- commentary TB (NSP p. 463, scan 0473; this lemma is absent from our OCR'd TB, now sk.2756.t1, re-filed from sk.2753.t1 on 2026-10-05): 'dhātoḥ' from 'dhātor ekācaḥ', 'bhāvakarmaṇoḥ' from 'ciṇ bhāvakarmaṇoḥ'. Same as BM; followed.
- commentary BM: in 'laḥ karmaṇi ca bhāve ca' (SK 2152) the word bhāva is used etymologically (yaugika) for bhāvanā, and utpādanā is added because bhāvanā also means 'thought'; utpādanā = activity conducive to coming-into-being (utpattyanukūlo vyāpāraḥ), which is no different from the dhātu-meaning (kriyā). 'sā ca dhātutvena…': pac etc. by the form dhātu-ness denote this general action, and by pac-ness etc. the particular result (viklitti etc.). 'anūdyate': the lakāra restates what is already denoted, as the dual does in 'dvau'. Followed: bhāva rendered 'bhāvanā, the act of bringing about', and anūdyate as 'restated'.
- commentary TB (sk.2756.t1; opening lemmas on NSP p. 463, scan 0473, missing from our OCR): bhāva is from causative bhū 'to come into being' + ac; 'utpādanā kriyā' shows that causative bhū means the same as plain kṛ; dhātutva is the delimiter of denoting-ness (vācakatāvacchedaka), kriyātva the delimiter of what is denoted. Agrees with BM; followed.
- commentary TB (sk.2756.t1): co-reference of a lakāra is possible only where it denotes agent or karma, not bhāva; the third person is still used because 'śeṣe prathamaḥ' (SK 2165) means 'the third person where the second and first do not apply'. On 'ekavacanam eva' TB says this is a general statement only (prāyovāda): the Bhāṣya's 'uṣṭrāsikā āsyante, hataśāyikāḥ śayyante' has a plural in bhāva. TB then reports the Manoramā's different account, which saves 'ekavacanam eva': there āsikāḥ and śāyikāḥ are second-case plurals, being karman as qualifiers of the action (kriyāviśeṣaṇa), and they are not neuter singular because the 'striyāṃ ktin' heading fixes the feminine ('manoramāyāṃ tu āsikāḥ śāyikā iti ca dvitīyābahuvacanaṃ kriyāviśeṣaṇatvena karmatvāt …'). Both views recorded (§16); the English keeps Bhaṭṭoji's unqualified 'only the singular'.
- commentary BM: sattva = a substance (dravya), fit to connect with gender and number; action denoted by a tiṅ is not such, whereas action denoted by a kṛt is (pākau, pākāḥ — Bhāṣya: 'kṛdabhihito bhāvo dravyavat prakāśate'). 'tasya autsargikatvena': per the Bhāṣya, 'dvyekayor dvivacanaikavacane' (SK 186) can be restated as 'ekavacanam; dvibahuṣu dvibahuvacane', so the singular is the default that does not need the number one. BM gives no 'prāyovāda' qualification (contrast TB). Followed for 'non-substance' and 'general one'.
- commentary BM: 'anabhihite': in a bhāva-lakāra the agent is not denoted by the tiṅ, hence the third case; 'tvayā mayā…' = 'becoming that has you, me, others as agent'. Followed.