Grammar

Words are stacked, not just inflected

Tamil is agglutinative: a word is a root with one or more suffixes attached in sequence, and each suffix carries one piece of meaning. In Sanskrit, a single ending fuses case, number and gender into one piece you can't divide (see Sanskrit Grammar). There is no upper limit on how many suffixes can stack, so ordinary Tamil words can translate to whole English clauses:

போகமுடியாதவர்களுக்காக (pōkamuṭiyātavarkaḷukkāka): eight morphemes, one word, "for the sake of those who cannot go."

Nine noun cases: one more than Sanskrit's eight

A case is just another suffix in the stack (root + optional plural -kaḷ + case ending). The extra case, beyond Sanskrit's eight (see Sanskrit Grammar), is the sociative, "along with". Sanskrit folds it into the instrumental.

Locative and dative each choose between two families of suffixes, depending on whether the noun is "rational" (people, deities) or "irrational" (everything else). Sanskrit has nothing like this. The same distinction runs through the gender system, below.

Five genders, not three: rational/irrational crossed with number

Sanskrit's masculine, feminine and neuter (see Sanskrit Grammar) sort every noun by grammatical gender alone. Tamil's pā (பால்) sorts by rationality first: only humans and deities get a true masculine/feminine split. It then crosses that with number, giving five categories instead of three:

Even a named female animal is grammatically irrational (neuter), not feminine. Gender agreement follows personhood, not biological sex.

Verbs stack the same way nouns do

Tamil has no single conjugation paradigm like Sanskrit's thematic-vowel classes. Tense, aspect, and person/number/gender are each their own suffix, added in a fixed order after the root:

அழிந்துக்கொண்டிருந்தேன் (aḻintukkoṇṭiruntēṉ): "I was being destroyed." Person/number/gender always comes last. It uses the same oblique pronoun forms found elsewhere in the sentence: -ēṉ (1st singular), -āy (2nd singular), -āṉ/-āḷ (3rd masculine/feminine singular), -ōm (1st plural). These are recognisably the same personal markers, reused as a suffix instead of a separate word. Sanskrit's verb endings are historically related to its pronouns too, but that is no longer visible in the language.

Puṇarcci: sandhi at the seams of agglutination

Every suffix boundary above is a possible sandhi site. Tamil's own puṇarcci (புணர்ச்சி) smooths the join much as Vedic Sanskrit sandhi does (see Sanskrit Grammar): it inserts a glide, doubles a consonant or drops a vowel so the result is easy to say.

One pronoun distinction Sanskrit doesn't mark

Tamil splits the first-person plural into an inclusive and an exclusive "we": நாம் (nām) if the listener is included, நாங்கள் (nāṅkaḷ) if not. Neither Sanskrit nor English marks this.