After the verbs beginning with jvala 'to shine' and ending with kasa 'to go', when used without a preposition, the affix ṇa is optionally used.,
The word इति in ज्वलति indicates beginning. These are about 56 verbs, all belonging to the Bhvadi class. See No. 804 to 860 in the Dhatupatha, Bombay Edition in the Appendix to Sidhanta Kaumudi.
This debars the affix अच्; as ज्वालः or ज्वलः; चालः or चलः.
The affix ण (अ) having an indicatory ण्, causes the vriddhi of the penultimate अ. When the affix ण is not used, then अच् is used and we have the other form. But compound verbs take अच्; as प्रज्वलः 'luminous'.
Vart:- The verb तन 'to stretch' must be included in this list, and it takes the affix ण; as अवतान. The conditions 'option' and 'without preposition' do not apply in this case. The verb तन् necessarily takes this affix, though compounded with an upasarga.,