The ik vowels which replace the semi-vowels yaṇ are called samprasāraṇa,
This defines the word samprasarana. It is the name given to the change of semi-vowels into vowels. The pratyahara ik includes the four simple vowels ई, उ, ऋ and लृ, and their corresponding semi-vowels are य्, व्, र्, and ल् included in the pratyahara yan. The word samprasarana is properly the name of the vowel which has replaced the semi-vowel. Thus the past participle of स्वप् 'to sleep,' is formed by adding the nishtha affix क्त (see sutra 1.1.26). So that we have स्वप् + त. But there is a rule 6.1.15 by which there is samprasarana of the व of स्वप् before the कित् affixes, and we have the form सुप्तः 'slept.' Similarly from वद् - उदितः, यज् - इष्टम्, व्यध् - विद्धः, ग्रह् — गृहीतम् — प्रछ्- पृष्टम्. The term samprasarana is also employed to designate the whole process of the change of the semi-vowels into vowels as in 6.1.13; 6.4.131.,