If you’d like Grammarly to stop flagging a particular spelling as incorrect, you can add the word to your personal dictionary by clicking the Add to dictionary button. Clicking it will add this word to your dictionary and prevent it from being marked as a mistake in the future.
The Add to dictionary button is indicated in this screenshot:
You can access your personal dictionary at any time to add or remove words. You can also add any words that you’d prefer Grammarly not to flag as being used incorrectly.
To access this feature, sign in to your account, go to Account, and then select Customize.
To remove a word from your personal dictionary, please click Account > Customize. Then, hover over the word that you wish to remove and click on the trash can icon that will appear next to it:
Note: Words containing symbols other than English language letters cannot be added to your Grammarly dictionary. Multiple words separated by spaces also cannot be added.