Tamil language grammar: the areas Thiruttham checks, and how
Tamil grammar is a large subject. This page is a map of the parts of formal written Tamil that Thiruttham checks, how each part is checked, and where it does not check yet. It is not a grammar textbook. If you want to learn a rule, start with the rule pages: some rules have their own page with examples, exceptions and sources, and the links below lead to the ones that exist.
Thiruttham checks in two layers. Fixed rules are written code that runs in your browser and gives the same answer every time. The AI-assisted check handles mistakes that depend on what the sentence means, and it needs a sign-in. Every suggestion says which one made it.
| Area | How it is checked |
|---|---|
| Consonant doubling (ottru) | Fixed rules |
| A doubling written by mistake | Fixed rules |
| Standard spellings and typing slips | Fixed rules |
| Spoken and written forms | Fixed rules |
| Similar-sounding letters | AI-assisted check, after sign-in |
| Agreement between subject and verb | AI-assisted check, after sign-in |
| Spoken forms beyond the list | AI-assisted check, after sign-in |
| Doubling where a rule cannot decide | AI-assisted check, Pro and 7-day trial |
| Cases not covered yet | Not checked today |
| Two rules being rebuilt | Not checked today |
Areas checked by fixed rules
Consonant doubling (ottru)
In formal writing, the hard consonant that starts the next word doubles after certain words and endings (this is the doubling, ottru mikum, as distinct from the dotted consonant, which is also called ottru). Thiruttham has fixed rules for listed cases: after அந்த, இந்த and எந்த; after ஆக and என; after the object ending ஐ and the dative ending கு in the listed forms; after அனைத்து; and after certain verb forms. Cases outside the lists are not checked, so a text with no suggestions can still contain a missing doubling.
A doubling written by mistake
The opposite slip: a consonant is doubled where the form does not take one. For the listed verb forms, Thiruttham suggests taking the extra consonant away.
Standard spellings and typing slips
A short list of common misspellings, each with its standard form, and a closed list of frequent words checked for a pulli (the dot above a consonant) that is missing or in the wrong place. Both are lists, not a dictionary, so a rarer word is not checked.
Spoken and written forms
Speech and formal writing differ in many words and endings. A list of 45 common spoken words and endings is checked, and Thiruttham suggests the written form for each. It is on by default and you can turn it off, which suits dialogue. The list covers common forms and may not match every region's speech.
Areas checked by the AI-assisted check
These need a sign-in. On the free plan the AI reads the first 500 words of a text, the first 5 AI corrections of each day are shown in full, and further suggestions are marked with a dotted underline. The AI shows an edit only when it is confident, so it can miss a mistake, and it can be wrong; that is why nothing changes until you accept it.
Similar-sounding letters
Words that differ by one letter, such as ல, ள and ழ, can have different meanings, and which one is right depends on the sentence. The AI-assisted check proposes an edit only when it is confident, so it can miss a mistake, and it can be wrong. The pair page lists each pair with its meaning and an example sentence.
Agreement between subject and verb
Whether the verb agrees with its subject in gender and in number depends on the sentence. The AI-assisted check proposes a repair only when it is confident, and it can be wrong.
Spoken forms beyond the list
For spoken words that are not on the list of 45, the AI proposes a written form only when it is confident.
Doubling where a rule cannot decide
After other words that end in ஐ or கு, whether the next consonant doubles depends on the sentence. On Pro and the 7-day trial, a second AI step answers yes or no for each such case, and a suggestion is shown only on a yes. It can miss a case, and it can be wrong.
Areas not checked today
A text with no suggestions can still contain mistakes. These are the areas where Thiruttham does not check today.
Cases not covered yet
Cases of doubling outside the lists above are not checked today. AI suggestions for the glide letters that join words (one kind of sandhi, how words join) were switched off because they were not reliable enough, and the AI choice between the object ending ஐ and the dative ending கு is being built. These are not checked today, so a text with no suggestions can still contain these mistakes.
Two rules being rebuilt
Two fixed rules gave too many wrong suggestions in testing and were switched off: doubling after எட்டு and பத்து, and the check for words that begin with ண or ன. They gave wrong suggestions on names as well as on other words. They are not checked today.
Both the fixed rules and the AI can be wrong or miss a mistake. You can dismiss any suggestion, add a word to your protected list (it needs a sign-in) so it is never changed, or report a wrong correction.
Check your own writing
The free check box on the Tamil grammar checker page runs the fixed rules on your text in your browser, with no account. The guide to formal Tamil shows the spoken and written forms side by side.
Which parts of Tamil grammar does Thiruttham check?
Consonant doubling after listed words and endings, a doubling written by mistake, standard spellings, a pulli missing or misplaced in common words, and the written forms of listed spoken words are checked by fixed rules. Similar-sounding letters, agreement between subject and verb, and spoken forms beyond the list are checked by the AI-assisted check after sign-in. The table above shows which is which.
Does Thiruttham teach Tamil grammar?
Not as a course. It checks the text you wrote and gives the reason for each suggestion. Where a rule has its own page, that page explains the rule with examples and sources.
Is checking free?
The fixed rules are free, run in your browser and need no account. The AI-assisted check needs a sign-in; on the free plan the first 5 AI corrections of each day are shown in full. The pricing page has the details.
Can it be wrong, or miss a mistake?
Yes. Both layers can be wrong, and a text with no suggestions can still contain mistakes. Nothing changes until you accept it.