Sanskrit swar sandhi (vowel sandhi) follows SPECIFIC, RULE-governed patterns: deergh sandhi (similar SHORT+similar vowel → the LONG version, e.g., देव+अर्चन combining 'अ'+'अ'→'आ'), guna sandhi (अ/आ + इ/ई → ए; अ/आ + उ/ऊ → ओ, e.g., देव+इंद्र → देवेंद्र), and vriddhi sandhi (अ/आ + ए/ऐ → ऐ; अ/आ + ओ/औ → औ).

• ›Recognizing these as SANSKRIT's MORE elaborate, RULE-DENSE swar sandhi system (compared to Hindi's SIMPLER version covered in the Hindi subject) is the chapter's foundational comparative point
• ›These RULES are FOUNDATIONAL to Sanskrit's grammar, with MANY Hindi sandhi rules DERIVED from these Sanskrit originals