मिदचोऽन्त्यात्परः

This sutra explains the use of the indicatory म्. The augments having an indicatory म्, technically called मित् augments, are placed immediately after the final vowel of a word. Thus there is an augment called नुम्, in which उ and म् are इत्, and the actual augment is न्. When, therefore, it is said \let नुम् be added to the word,\ the letter न् is added after the last vowel. Thus the plural of पयस् 'milk' is formed in the following way :- पयस् + नुम् + इ 7.1.72 = पयान्सि 6.4.8. Here न् is added between य and स् i.e. after the अ of य, which is the final vowel of the word: and before this न् at the preceding short vowel is lengthened. Similarly मुच् + श + ति 3.1.77 = मुच् + नुम् + श + ति 6.1.59 = मुञ्चति । Similarly विरुणद्धि.

The word अचः is in the genitive case, having the force of nirdharana or specification; it has the force of the plural, though exhibited in the singular, being taken as representing the class. The meaning is 'among the vowels.' This sutra is an exception to sutras 1.1.49 and 3.1.2, by which an affix is added at the end of the word exhibited in the 6th case.

There is, however, an exception, in the case of the root मस्ज्, in which the augment नुम् is added not after the last vowel अ of म, but between स् and ज्. The result of adding the augment नुम् between स् and ज् is, that sutra (VIII. 2. 29.) applies, and the स् is elided. Thus मस्ज् + ता = मस्ज् + नुम् + ता 7.1.60 = मस्न्ज् + ता = मञ्ज् + ता 7.2.29 = मङ्क्ता \He will immerse\. So also मग्नः 'immersed,' मग्नवान्, मङ्क्तुम्.,