Of a root beginning with da , the dha is substituted for ha before a jhal (all consonant except semi-vowels and nasals) letter or at the end of a word.,
For the final ह् of a द-beginning root, घ is substituted under similar circumstances. As दग्धा, दग्धुम्, दग्धव्यम्, काष्ठधक्, दोग्धा, दोग्धुम्, दोग्धव्यम्, गोधुक्, from दह् and दुह् ॥ For the त् of the affixes तृ &c. ध is substituted by 8.2.40, before which, the घ becomes ग by 8.4.53. For the घ in काष्ठदघ् is substituted ग by 8.2.39, or क् by 8.4.56, and द becomes ध by 8.2.37.
Why do we say \of a root beginning with द\? Observe लेढा, लेढुम्, लेढव्यम्, गुडेलिट् ॥
The force of the genitive case in धातोः is not to make it in apposition with the word दादेः, but it has the force of denoting a part as related to the whole: so that it means \the word which begins with द and forms part of a root, for the ह of such a part is substituted घ.\ What does follow from it? The letter घ is substituted in अधोग् also, which begins with अ ॥ For without the above explanation (धातोरवयवो यो दादिशब्दस्तदवयवस्य हकारस्य &c), the घ would have come in examples like मास्म धोक्, without the augment अ, but not where there was the augment अ ॥ Moreover, that it is an अवयवयोगा षष्ठी will appear necessary in sutra 8.2.37.
If it has the force of denoting a 'portion or member', how do you explain the forms दोग्धा, दोग्धुम्, for here no portion is taken but the whole word? This will be explained on the maxim of व्यपदेशिवद् भावः \An operation which affects something on account of some special designation, which for certain reasons attaches to the latter, affects likewise that which stands alone, and to which therefore, just because the reasons for it do not exist, that special designation does not attach\. (व्यपदेशिवद् एकस्मिन्) ॥ Or we may explain the sutra, by saying 'that root which begins with द् in its original enunciation in Dhatupatha'? Thus in original enunciation the root is लिह् not beginning with द ॥ If a Derivative root be formed from it like दामलिह्य (दामलिहमिच्छति = दामलिह्यति), it is a root which begins with द; the ह of this Denominative root, however, will not be changed to घ, for it is not a root of upadesa_. Therefore, when we add क्विप् to this root, we get दामलिट् by 8.2.31, and not दामलिक् ॥,