The affix inuṇ comes after a root in denoting condition when co-extensiveness is meant.,
The word अभिविधि means co-extensiveness, that is to say, the complete comprehension or relation between the action and the quality. Thus सांराविणम् 'a general or tumultuous uproar'; सं + कूट् + इन् + अण (V. 4. 15.) and (VI 4. 164) = 'a general confusion'; so सांस्राविणम् 'a general flow or stream'.
Why do we say 'when meaning co-extensiveness'? Observe सङ्कोटः, संरावः, सन्द्रावः ।
Why do we use the word भाव again in this sutra, when its anuvritti was already flowing from sutra 3.3.18? The object is that the वाऽसरूप rule 3.1.94 should not apply here and hence घञ् never comes in this sense. Patanjali says that the repetition is for the sake of indicating that in neuter gender, when co-extensiveness is expressed, the affixes क्त &c. are prohibited; so that the affixes क्त &c. should not come in the neuter with the force of भाव ।
The separateness of this sutra is for the same purpose as the last aphorism. The affix ल्युट् is not, however, prohibited; as सङ्कुटनम्. See rule कृत्यल्युटो बहुलं 3.3.113. The affix इनुण् (the operative part being इन्) forms but an imaginary stem, which does not become real and complete till it takes the affix अण् by 5.4.15, as shown above.,