Weak Masculine Nouns (N-Declension)

The noun itself changes shape — a productive Telugu habit, not a short exception list

Unlike Tamil, where a noun's stem never changes shape and only suffixes attach onto it, Telugu masculine human nouns ending in -డు genuinely do alternate their stem before oblique-case suffixes: బాలుడు (baaludu, 'boy', nominative) becomes బాలుడి/బాలుని (baaludi/baaluni) in every other case, much like German's der Junge → den/dem/des Jungen. The real difference from German is productivity: German's weak declension is a small, closed, memorized list (Junge, Student, Löwe, Name, and a few dozen more), while Telugu's -డు stem alternation is a broad, predictable pattern covering nearly every masculine human agentive noun of that shape — a rule, not an exception list. Sanskrit-derived nouns like విద్యార్థి ('student') and non-human nouns like సింహం ('lion') or పేరు ('name') don't follow this pattern at all, so the comparison is real but narrower than it first looks.