245. Final radical i and u

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).