One of the commonest types of finite verbs is the verb marked for tense and for person, number and gender (PNG). Verbs which are marked for PNG are always marked for tense, although some tense-marked verbs are not marked for PNG.Some LT verbs may consist of a stem plus PNG markers, and the absence of a tense marker implies negation; but this is not a productive process in ST. A few relic forms, such as ´Ôغԣ kaanoom `I don't see (anything) ' (lit. `we do not see') remain in the language as idiomatic phrases. Such PNG-less, tense-marked verbs are called `non-finite verbs'.
Verbs marked for tense and PNG have the following structure: They consist of the verb stem, usually identical with the non-polite imperative stem, plus a tense marker and finally a PNG marker.
As is obvious from these examples, not all verbs have the same present tense marker. In fact, Tamil verbs must be divided into several classes, depending on which tense-markers they require.Because of Tamil spelling conventions, certain consonant clusters are usually avoided by adding epenthetic Ë u between consonants; one such convention is that the LT present tense marker ¡´Õ± is usually written ¡Þ± whenever ST is written (in novels etc.) even though phonetically it is [kkr], and our transliteration is kkr.
Depending on one's linguistic bias, Tamil verbs can be arranged into as few as three or as many as thirteen classes, according to the consonantal alternations which occur when tense markers are added to the stem. For pedagogical purposes, it is probably best to set up about five classes and handle exceptional verbs by applying certain rules to them. Verbs are listed below by stems (identical in most cases to the imperative) followed by the English gloss, then the infinitive, the present, the past, and the future.