Hi Tiyo, Sandhi (सन्धिः sandhí "joining") is a cover term for a wide variety of phonological processes that occur at morpheme or word boundaries. Examples include the fusion of sound across word boundaries, as its name implies, and the alteration of sounds due to neighboring sound or due to the grammatical function of adjacent words. So if you combine two words like प् + र it will be combined as प्र (Pra) If you will add words : प + र = पर (par) but if you will write प् ( look at the small sign under (प्) it is called (halant, it shows the sound (rrrrrrrrr)) so if you will combine these both words ( प् + र ) it will be converted in pra(प्र ). Same will be applied on र् + प = र्प. Few Examples: प्रश्न (prashn) [ Question] , सर्प (sarp) [Snake], प्रयत्न(praytn) [Effort] etc. Thanks ,