The augment t is added to the particle ā and the prohibitive particle mā , when cha follows an in a continuous text.,
The Particle आ has the four senses of 1. littleness (ईषदर्थे) 2. with verbs, as a prefix (क्रियायोगः) 3. the limit inceptive (अभिविधि) and 4. the limit exclusive (मर्यादा). This sutra ordains तुक् necessarily, where by 6.1.76, it would have been optional. Thus ईषच्छाया = आच्छाया; 2. With verbs:-as आच्छादयति, 3 and 4., आच्छायायाः, आच्छायम् ॥ So also the negative particle मा, as, माच्छैत्सीत्, माच्छिदत् ॥ The ङ् in आङ् and माङ् shows that आ when used as a Gati and a Karmapravachaniya and मा when used as a negative particle are meant. Therefore, the त् is not necessary in the following :-आछाया मानयति, प्रमाछन्दः ॥ The तुक may be optionally added in these as आच्छाया and प्रमाच्छन्दः ॥ The आ here has the force of recollection (स्मरण); आछाया \Oh the shade\. The word प्रमा is formed from the verbal root माङ् by the prefix प्र and the affix अङ् 3.3.106 with the feminine affix टाप्, and the word ending in टाप् has not the indicatory ङ् ॥,