a. In root and suffix-syllables, instead of guṇa: thus, stāúti from √stu, sákhāyam from sákhi, ánāiṣam from √nī, ákārṣam and kāráyati and kāryà from √kṛ (or kar), dātā́ram from dātṛ́ (or dātár).
b. Especially often, in initial syllables in secondary derivation: thus, mānasá from mánas, vāidyutá from vidyút, bhāumá from bhū́mi, pā́rthiva from pṛthivī́ (1204).
But—
240. The guṇa-increment does not usually take place in a heavy syllable ending with a consonant: that is to say, the rules prescribing guṇa in processes of derivation and inflection do not apply to a short vowel which is “long by position”, nor to a long vowel unless it be final: thus, cétati from √cit, but níndati from √nind; náyati from √nī, but jī́vati from √jīv.
a. The vṛddhi-increment is not liable to this restriction.
b. Exceptions to the rule are occasionally met with: thus, ehá, ehas from √īh; heḍáyāmi, héḍas, etc., from √hīḍ; coṣa etc. from √cūṣ; óhate etc. from √ūh consider; and especially, from roots in īv: didéva deviṣyati, dévana, etc., from √dīv; tiṣṭheva from √ṣṭhīv; sreváyāmi, srévuka, from √srīv — on account of which it is, doubtless, that these roots are written with iv (div etc.) by the Hindu grammarians, although they nowhere show a short i, in either verb-forms or derivatives.
c. A few cases occur of prolongation instead of increment; thus, dūṣáyati from √duṣ, gū́hati from √guh.
The changes of ṛ (more original ar or ra) are so various as to call for further description.
241. The increments of ṛ are sometimes ra and rā, instead of ar and ār: namely, especially, where by such reversal a difficult combination of consonants is avoided: thus, from √dṛç, drakṣyā́mi and ádrākṣam; but also pṛthú and prath, pṛch and prach, kṛpā́ and ákrapiṣṭa.
242. In a number of roots (about a dozen quotable ones) ending in ṛ (for more original ar), the ṛ exchanges both with ar, and more irregularly, in a part of the forms, with ir — or also with ur (especially after a labial, in pṛ, mṛ, vṛ, sporadically in others): which ir and ur, again, are liable to prolongation into īr and ūr. Thus, for example, from tṛ (or tar), we have tarati, titarti, tatāra, atāriṣam, by regular processes; but also tirati, tīryati, tīrtvā, -tīrya, tīrṇa, and even (V.) turyāma, tuturyāt, tarturāṇa. The treatment of such roots has to be described in speaking of each formation.
a. For the purpose of artificially indicating this peculiarity of treatment, such roots are by the Hindu grammarians written with long ṝ, or with both ṛ and ṝ: no ṝ actually appears anywhere among their forms.
