Reduplication.
588. The derivation of conjugational and declensional stems from roots by reduplication, either alone or along with other formative elements, has been already spoken of (259), and the formations in which reduplication appears have been specified: they are, in primary verb-inflection, the present (of a certain class of verbs), the perfect (of nearly all), and the aorist (of a large number); and the intensive and desiderative secondary conjugations contain in their stems the same element.
589. The general principle of reduplication is the prefixion to a root of a part of itself repeated — if it begin with consonants, the initial consonant and the vowel; if it begin with a vowel, that vowel, either alone or with a following consonant. The varieties of detail, however, are very considerable. Thus, especially, as regards the vowel, which in present and perfect and desiderative is regularly shorter and lighter in the reduplication than in the root-syllable, in aorist is longer, and in intensive is strengthened. The differences as regards an initial consonant are less, and chiefly confined to the intensive; for the others, certain general rules may be here stated, all further details being left to be given in connection with the account of the separate formations.
590. The consonant of the reduplicating syllable is in general the first consonant of the root: thus, पप्रछ् paprach from √प्रछ् prach; शिश्रि çiçri from √श्रि çri; बुबुध् bubudh from √बुध्. But —
a. A non-aspirate is substituted in reduplication for an aspirate: thus, दधा dadhā from √धा; बिभृ bibhṛ from √भृ bhṛ.
b. A palatal is substituted for a guttural or for ह् h:
