In the case of Vocative, the singular number of the 1st case-affix is called smabuddhi,
The vocative singular is called sambuddhi, when it is employed in the vocation. Thus 6.1.69 declares 'after an inflectien base ending in एङ् or in a short vowel, a consonant is elided if it be that of 'Sambuddhi' as हे राम ॥,