b. The (quotable) ṝ-roots are 2 kṛ strew, 1 gṛ sing, 2 gṛ swallow, 1 jṛ wear out, tṛ, 1 çṛ crush.
c. The (quotable) ṛ and ṝ-roots are ṛ, 1 dṛ pierce, 1 pṛ fill, 1 mṛ die, 2 vṛ choose, stṛ, hvṛ.
d. Forms analogous with these are sometimes made also from other roots: thus, cīrṇa, cīrtvā, carcūryá, from √car; spūrdhán and spūrdháse from √spṛdh.
243. In a few cases ṛ comes from the contraction of other syllables than ar and ra: thus, in tṛta and tṛtīya, from ri; in çṛṇu, from ru; in bhṛkūṭi, from rū.
Vowel-lengthening.
244. Vowel-lengthening concerns especially i and u, since lengthening of a is in part (except where in evident analogy with that of i and u) indistinguishable from its increment, and ṛ is made long only in certain plural cases of stems in ṛ (or ar: 369 ff.). Lengthening is a much more irregular and sporadic change than increment, and its cases will in general be left to be pointed out in connection with the processes of inflection and derivation: a few only will be mentioned here.
245. a. Final radical i and u are especially liable to prolongation before y: as in passive and gerund and so on.
b. Final radical ir and ur (from variable ṛ-roots: 242) are liable to prolongation before all consonants except those of personal endings: namely, before y and tvā and na: and in declensions before bh and s (392). Radical is has the same prolongation in declension (392).
246. Compensatory lengthening, or absorption by a vowel of the time of a lost following consonant, is by no means common. Certain instances of it have been pointed out above (179, 198 c, d, 199 d, 222 b). Perhaps such cases as pitā for pitars (371 a) and dhanī for dhanins (439) are to be classed here.
247. The final vowel of a former member of a compound is often made long, especially in the Veda. Prolongations of final a, and before v, are most frequent; but cases are found of every variety. Examples are: devāvī́, vayunāvíd, prāvṛ́ṣ, ṛtāvasu, índrāvant, sadanāsád, çatā́magha, viçvā́nara, ékādaça; apījū́, parīṇáh, vīrúdh, tuvīmaghá, tvíṣīmant, çáktīvant; vasūjū́, anūrúdh, sūmáya, purūvásu.
248. In the Veda, the final vowel of a word — generally a, much less often i and u — is in a large number of cases prolonged. Usually the prolongation takes place where it is favored by the metre, but sometimes even where the metre opposes the change (for details, see the various Prātiçākhyas).
Words of which the finals are thus treated are:
