Don’t let bad grammar take the heartfelt sentiment out your note to Mom this Sunday. Like me, you may wonder where the apostrophe goes—is it Mother’s Day or Mothers’ Day?

As is often the case, Google the word and you’ll get a ton of spelling options: Mother’s Day, Mothers’ Day and even the apostrophe-free Mothers Day. Search no more, Mother’s Day is the grammatically correct way. But why?

There are millions of moms out there who are hoping for breakfast in bed and a bouquet of roses—not just one. Some folks are even so lucky as to have more than one mom. In addition to your biological mom, you could have a stepmom, a foster mom, a mother-in-law, an adopted mom, two lesbian moms . . . the possibilities of the modern family are virtually endless. So why is Mother’s Day focused on just one mom?

According to the Grammarphobia Blog, Anna Jarvis, the woman largely behind this holiday, wanted the day to “honor one’s own mother, not mothers in general.” And so the apostrophe fits snuggly between the r and the s, and nowhere else.

So go ahead and make your mom proud and wish her a “Happy Mother’s Day” this Sunday!