Writing & Editing Grammar Girl explains when to use affect vs. effect Mignon Fogarty, more commonly known as Grammar Girl, provides a quick and easy way to remember the difference between these often confusing words. By Ragan StaffJan. 14, 2014 SHARE One of the most common grammar questions Mignon Fogarty, more commonly known as Grammar Girl, gets asked is this: When do you use affect and effect? To read the full story, log in. Become a Ragan Insider member to read this article and all other archived content. Sign up today Already a member? Log in here. Learn more about Ragan Insider.