387. The vowel a is lengthened

The vowel a is lengthened in strong cases as follows:

1. Of the roots vac, sac, sap, nabt, ças, in a few instances (V.), at the end of compounds; — 2. Of the roots vah and sah, but irregularly; see below, 403–5; — 3. Of apwater (see 393); also in its compound rītyàp; — 4. Of pad, foot: in the compounds of this word, in the later language, the same lengthening is made in the middle cases also; and in RV. and AV. the nom. sing. neut. is both -pat and -pāt, while RV. has once -pāde, and -pādhbis and -pātsu occur in the Brāhmaṇas; — 5. Of nas nose (?nā́sā nom. du. fem. RV., once); — 6. Sporadic cases (V.) are: yāj (?), voc. sing.; pāthás and -rāpas, accus. pl.; vánīvānas, nom. pl. The strengthened forms bhājand rāj are constant, through all classes of cases.