Tamil nouns (and pronouns) are classified into two super-classes (tiṇai)—the "rational" (uyartiṇai), and the "irrational" (akṟiṇai)—which include a total of five classes (pāl, which literally means ‘gender'). Humans and deities are classified as "rational", and all other nouns (animals, objects, abstract nouns) are classified as irrational. The "rational" nouns and pronouns belong to one of three classes (pāl)—masculine singular, feminine singular, and rational plural. The "irrational" nouns and pronouns belong to one of two classes: irrational singular and irrational plural. The pāl is often indicated through suffixes. The plural form for rational nouns may be used as an honorific, gender-neutral, singular form.
Suffixes are used to perform the functions of cases or postpositions. Traditional grammarians tried to group the various suffixes into eight cases corresponding to the cases used in Sanskrit. These were the nominative, accusative, dative, sociative, genitive, instrumental, locative, and ablative. Modern grammarians argue that this classification is artificial, and that Tamil usage is best understood if each suffix or combination of suffixes is seen as marking a separate case. Tamil nouns can take one of four prefixes, i, a, u, and e which are functionally equivalent to the demonstratives in English.
Tamil verbs are also inflected through the use of suffixes. A typical Tamil verb form will have a number of suffixes, which show person, number, mood, tense, and voice.
- Person and number are indicated by suffixing the oblique case of the relevant pronoun. The suffixes to indicate tenses and voice are formed from grammatical particles, which are added to the stem.
- Tamil has two voices. The first indicates that the subject of the sentence undergoes or is the object of the action named by the verb stem, and the second indicates that the subject of the sentence directs the action referred to by the verb stem.
- Tamil has three simple tenses—past, present, and future—indicated by the suffixes, as well as a series of perfects indicated by compound suffixes. Mood is implicit in Tamil, and is normally reflected by the same morphemes which mark tense categories. Tamil verbs also mark evidentiality, through the addition of the hearsay clitic ām.
Traditional grammars of Tamil do not distinguish between adjectives and adverbs, including both of them under the category uriccol, although modern grammarians tend to distinguish between them on morphological and syntactical grounds. Tamil has a large number of ideophones that act as adverbs indicating the way the object in a given state "says" or "sounds".
Tamil does not have articles. Definiteness and indefiniteness are either indicated by special grammatical devices, such as using the number "one" as an indefinite article, or by the context. In the first person plural, Tamil makes a distinction between inclusive pronouns நாம் nām (we), நமது namatu (our) that include the addressee and exclusive pronouns நாங்கள் nāṅkaḷ (we), எமது ematu (our) that do not.