Lesson 22: Formation of Past
Active and Passive Participles

Form and meaning are related in 1) the infinitive and general future on one hand, and 2) the gerund and past participle on the other. Just as a root usually takes the same form in both the general future and the infinitive (e.g., इष् एषि-तुम् एषि-ष्यति)—which are both future-oriented—so will a root usually take the same form in the gerund and past participle—both of which are past-oriented (e.g., वस् उषि-त्वा उषि-त).
  • The basic form of the past participle is (weak) root + (इ)त.
Thus, if you know the gerund (in -त्वा), you can usually easily derive the past participle (whether its root takes the -इ suffix or not). And because both suffixes (-त्वा and -त) begin with the same sound, their sandhi will be the same:
  • वस् — उषित्वा, “having dwelled,” उषित, “dwelled” 
  • मन् — मत्वा, “having thought,” मत, “thought”
  • नुद् — नुत्त्वा, “having pushed,” नुत्त, “pushed"
  • त्यज् — त्यक्त्वा, “having abandoned,” त्यक्त, “abandoned”
  • स्पृश् — स्पृष्ट्वा, “having touched,” स्पृष्ट, “touched”
  • गाह् — गाढ्वा, “having plunged,” गाढ, “plunged”
Note the following features and internal sandhi in the examples above:
  • Samprasāraṇam: वस् उषित, वद् उदित, यज् इष्ट, वह् ऊढ, प्रच्छ् पृष्ट
  • Nasal loss: मन् मत, गम् गत, नम् नत, रम् रत, कृन्त् कृत्त, दंश् दष्ट, शंस् शस्त
  • Final -च् (and sometimes -ज्) → -क् // त् : त्यज् त्यक्त, *पच् पक्त, मुच् मुक्त
  • Final -श् (and sometimes -ज्) → -ष्, which retroflexes a following त् :
    स्पृश् स्पृष्ट, इष् इष्ट, यज् इष्ट, कृष् कृष्ट, क्लिश् क्लिष्ट, तुष् तुष्ट, दंश् दष्ट, दिश् दिष्ट, दृश् दृष्ट, नश् नष्ट, पुष् पुष्ट, प्रच्छ् (= प्रश्) पृष्ट, विश् विष्ट
  • (non-द्)V(ह्) roots + त → (non-द्)VV(ढ), e.g., गाह् गाढ, रुह् रूढ, वह् ऊढ
  • +V → -V // -V: नुद् नुत्त, विद् वित्त
  • Aspiration and Voicing shifts onto following त : +V+A + त → +V-A + ध:
    दह् दग्ध, बुध् बुद्ध, लभ् लब्ध, वृध् वृद्ध 
Roots ending in -द् or -र्
The suffix for roots which end in a -द् or -र् is न. By sandhi, the final -द् will be assimilated to the following nasal, yielding -न्न (and a final -र् will retroflex the following nasal, yielding र्ण):
  • खिद् खिन्न, तुद् तुन्न, विद् विन्न, सद् सन्न, कॄ कीर्ण, etc.
10th Class (and Causal) Roots
The one major difference in roots’ forms before the gerund and past participle suffixes comes in the 10th class. While in the 10th class the gerund suffix is added to the full stem, the past participle suffix is added to the stem, minus -अय, e.g.:
  • 10th class gerund = stem + इत्वा — चिन्त् चिन्तयित्वा, चुर् चोरयित्वा
  • 10th class pp. = stem minus -अय + इत — चिन्त् चिन्तित, चुर् चोरित
The suffix here is always -इत because 10th class roots are always सेट्.