Best grammar checker for English.

Question

I am looking for a grammar checker for English. I know it will never be perfect but it can help me by pointing out a possible mistake I have to consider. The best free tool for this seems to be the one of Abiword that exists nowhere else (as far as I know). I have tried LanguageTool but it misses obvious errors like this one:
“It does not see this mistakes.”
(Wrong plural form for mistake).
Any suggestion? It would be nice if at least others look at what Abiword has done. Abiword only signal a possible error without trying to correct it but is already something valuable.

Answer 1

olive wrote:One of the reason I want a grammar checker is to write on these forums and obviously, I won't submit every posts I make for proofreading.
Understood.
Just a suggestion: if you're open to being corrected here, you could add something to your signature along those lines. Some people do.
I am a native French speaker and I have a commercial grammar checker for French that is able to correct about 90% of grammar mistakes and tell something stupid about 10% of the time. This is commercial and rather expensive, but it shows what is technically possible.
Technically possible? Maybe for French, but that doesn't say much about English. (I don't speak French, so I will consider generalities that apply to both Spanish and Latin.) Since English verbs typically come in only four-ish forms (walk, walks, walked, walking) and many words can be either nouns or verbs as the situation demands ("walk/walks" being a good example, but "mistake", from your first post, is another), there is a lot of room for ambiguity that software simply can't resolve.
Consider the sentence you used earlier, "It does not see this mistakes". An intelligent audience would probably realize "this mistakes" was meant to be a noun phrase and suggest "this mistake" (or "these mistakes"), but grammatically, "this mistakes" could be a (somewhat awkward) relative clause with "mistakes" being a verb and "this" a pronoun. Compare "I do not think it understands", in which "it understands" is the relative clause. If I read it that way, the "correction" becomes wrong.
True, it's unlikely that a real person would use "mistake" like that, but the point is, you can't disambiguate that sentence based purely on syntax; you have to have some idea what it means. And you need a lot of that semantic knowledge in order to spot errors 90% of the time.
My opinion of these tools is that they are very useful if you know how to use them; that is at each suggestion, think about twice and accept the correction if you know the software is right.
My experience has been that every single time a grammar checker "corrects" me, I am right and the software is wrong.[1] That's likely not true for everyone. But with sentences like the example above, you might just be running into the limit of what's possible to check, with existing technology, without throwing perfectly good English under the bus. I doubt there is any tool that checks English grammar with more than 50% accuracy.
[1] This is not quite fair. I have made subtle grammatical mistakes and found them because of grammar checkers. Nevertheless, the software invariably suggests "fixing" it in a way that either changes the meaning or actually makes the rest of the sentence un-grammatical.