After a verb which begins in a consonant and ends in a letter of ral pratyahāra and has as its penultimate i or ī and u or ū , the ktvā and san affixes are optionally kit ,
The wording of this sutra requires a little explanation. It consists of the following words:-
1. रलः ralah, ablative of रल् (after the consonants included in the Pratayahara ral i.e., all the consonants except य् y and व् v) :- Verbs having their final letter any single consonant except य् y and व् v.
2. व्युपधात् and means \after penultimate वी.\ It is a compound of वी + उपधा. The वी itself is a compound of उ + इ = वि, in the dual वी. Therefore the phrase means \after (verbs) having for their penultimate either इ i or उ u long or short.\
3. हलादेः means \beginning with a consonant.\
All these three words qualify the word \verb\ understood.
4. संश्च means \and san.\
The sutra means, those verbs which have a रल् letter in the end, a हल् in the beginning, and an इ, ई or उ, ऊ in their penultimate, may optionally treat the affixes ktva and san as कित्.
Thus दद्युत् 'to shine,' makes दद्युतित्वा or द्योतित्वा 'having shone,' लिख् 'to write' makes लिखित्वा or लेखित्वा.
Similarly in san affix we have लिलिखिषति or लिलेखिषति 'he wishes to write', दिदद्युतिषते or दिद्योतिषते 'wishes to shine.'
The rule does not apply if the verb ends in a letter other than रल्. As दिव् + क्त्वा = देवित्वा; its desiderative will be दिदेविषति. No option is allowed here.
Similarly there is no option when the penultimate vowel is not इ or उ. As वृत्त् + क्त्वा = वर्तित्वा Des. विवर्तिषते.
The rule also does not apply if the verb does not begin with a consonant. As एषित्वा and एषिषिषति. There is no option allowed here.
The rule does not apply if the क्त्वा and सन् are anit. As भुक्त्वा, बुभुक्षते.
In these 26 sutras the description of affixes which are treated like ङित् and कित् is comprised.,