https://techcrunch.com/2018/07/24/google-docs-gets-an-ai-grammar-checker/

You probably don’t want to make grammar errors in your emails (or blog posts), but every now and then, they do slip in. Your standard spell-checking tool won’t catch them unless you use an extension like Grammarly. Well, Grammarly is getting some competition today in the form of a new machine learning-based grammar checker from Google that’s soon going live in Google Docs.

These new grammar suggestions in Docs, which are now available through Google’s Early Adopter Program, are powered by what is essentially a machine translation algorithm that can recognize errors and suggest corrections as you type. Google says it can catch anything from wrongly used articles (“an” instead of “a”) to more complicated issues like incorrectly used subordinate clauses.