Grammarly has been available as a stand-alone product, a browser extension, and an add-in for Microsoft Word for Windows for years. Until now, the writing assistant was only compatible with the Windows version of Word. Mac users who wanted to integrate the AI-driven writing assistant into Word for Mac were not able to do so. The Mac add in will display grammatical, spelling, and rewrite suggestions as you type based on the tone you wish to set for the document.
Source: https://www.bleepingcomputer.com/news/software/grammarly-is-now-available-for-microsoft-word-on-mac/