Breaking down "suresh", Om thinks its two parts "sur" and "eesh" will combine into a matching…
Breaking down "suresh", Om thinks its two parts "sur" and "eesh" will combine into a matching vowel (like "i+i=ee"). His sister says two different vowels here combine into a third, new vowel. Who is right?
Who do you think is right? Pick one.
The answer: His sister is right, in "sur"+"eesh" the "a"+"ee" merge into "e"
Why
Om is trying to match this to the simplest sandhi rule — matching vowels merging into the same vowel ('आ'+'आ'='आ' from 'विद्यालय') — but which rule applies depends on exactly which two vowels are meeting, and here they are NOT the same vowel. 'सुर' ends in the inherent 'अ', and 'ईश' begins with 'ई'; when 'अ' is followed by 'इ' or 'ई', the two merge into a third, different vowel — 'ए' — not into either original vowel. So 'सुर'+'ईश' becomes 'सुरेश' ('अ'+'ई'='ए'). This is गुण संधि (gun sandhi), the same rule family seen earlier in 'देवेन्द्र' ('देव'+'इंद्र', 'अ'+'इ'='ए'). Test it: both 'देवेन्द्र' and 'सुरेश' follow the identical 'अ+इ/ई=ए' pattern, even though the specific vowels combining ('इ' vs 'ई') differ slightly. His sister is right: 'अ' and 'ई' merge into a new vowel, 'ए' — this is गुण संधि, not two matching vowels staying the same.
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