There is always elision of the s of the first person of the affixes that come in the room of that la which has an indicatory ṅ,
The tense-affixes having indicatory ङ् are four, namely, लङ्, लिङ्, लुङ् and लृङ् । In their case, the elision of स् is not optional as was the case in the last sutra, but compulsory. See the table already given. In other words, in the Imperfect, Potential, Aorist and Conditional, the स् is elided in the Ist person. Thus अपचाव, अपचाम। The word नित्यं 'always' is used in order to stop the anuvritti of the word 'optionally'.,