This classificatory scheme does not work perfectly for ST, however, so we have proposed additional subclassifications for certain of Graul's classes, notably verbs in classes II and VI, where stem-final front vowels trigger palatalization of the past tense markers ÿ¢ and ¢¢ to nj and cc, respectively. Verbs of classes II and VI whose stems do not meet these conditions are not specially marked, but those that do are marked IIb and VIb, respectively. Thus the verb ×»ÀÕ, II intr., with stem-final É triggering palatalization of the past marker ÿ¢ to nj in spoken is classified as IIb, and ¶Ù¾, VI tr., which has a palatalized past tense marker cc in ST, is classified as VIb.
In addition, in classes II, III, and V there are a number of irregular verbs that do not follow the regular rules in one or another tense form, so we have marked certain verbs as members of subclass IIc, or IIIb, or Vc, to try to fit them into the class they most closely resemble. Most irregularities or complexities of the Tamil verb are to be found in the past tense; were it not for these past tense problems, most Tamil verbs could be classified simply as ``strong" or ``weak", depending on whether they have doubled consonants in the present (¡´Õ±-) and future (¤¤) tense marker, or single consonants (´Õ±) and (Â/½). This strong-weak scheme is used by some scholars and in some pedagogical materials for Tamil as a general description of the verb, but it is not adequate to predict the details of the past tense. It is useful if the discussion centers on the formation of infinitives or of neuter futures, and the strong-weak distinction also correlates in some ways with transitivity and intransitivity. But this correlation is not perfectly regular and can only serve as a mnemonic device when the exact classification cannot be remembered.
In ST, subclassifying classes II, III, V, and VI into palatalizing, non-palatalizing, and otherwise irregular helps to take care of most areas where ST forms are different from Literary Tamil, but it does not take care of all. In some cases, ST verbs are members of totally distinct classes from their Literary Tamil counterparts, and this is particularly true of members of Literary Tamil classes I and V---Literary Tamil class I is a very small class, i.e. has very few members, and given that some of these Literary Tamil verbs are never used in ST, while other members shift to another class, class I as a spoken class is an almost empty set. There are, however, a few members that retain and duplicate the morphology of the Literary Tamil set, so it must be retained. The Literary Tamil verb ×¶², I tr. `do, make' changes to class II in ST: its past is senj- rather than the Literary Tamil ×¶²¢- seyd- (the verb ×½² `rain' also shifts to II in ST). But verbs like Çê `weep' and Ëê `plow' remain in class I in spoken, with pasts in d analogous to Literary Tamil single ¢ pasts: ÇêØ»¨ a= to0pt.25ex ##= by .25ex udeen `I wept.'