Pāṇini sūtras

The long vowel is substituted for a vocalised half-vowel a, i and u at the end of a stem, when it is preceded by a consonant which is a portion of the stem.

German Für einen vocalisirten Halbvocal (s. 6, 3, 139) im Auslaut enes Stammes wird, wenn ihm ein Consonant vorangeht, die Länge substituirt. (2)

1. ha+laḥह+लः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   hह्	haह	haह	hakāraहकार	hह् + plus aअ
   lल्	lल्	laḥलः	LL	lल् + plus aḥअः