The number of vowels in Tamil are recognized as 12, and the number of consonants recognized are 18. The current description mentions the number of consonants as 17. Apart from these there is a letter that is not considered either as a vowel or as a consonant. It is called 'aydham' in Tamil. It is not a vowel and hence does not conjugate with any consonant. It is not a consonant because it does not conjugate with any vowel. Of the vowels 10 are monophthongs and two are diphthongs. Five monophthong vowels (equivalent to a, e, i, o, u), are short forms and another five are their long forms sounded twice as long in duration. The two diphthong vowels are a+i and a+u. The 12 vowels conjugate with the 18 consonants to produce 216 conjugates. Ref: https://en.wikipedia.org/wiki/Tamil_language Look under section 'writing system'