Receiving a formal wedding invitation can sometimes come with a small mystery. Alongside the familiar choices for accepting or declining, some RSVP cards include a blank line beginning with a single capital “M.” It can look strangely incomplete, but it actually comes from a long-standing tradition in formal invitations.

The “M” is the beginning of the guest’s title. It is there so the person responding can complete the line with “Mr.,” “Mrs.,” “Miss,” or “Ms.” followed by their name. For example, a married guest named Sarah Johnson might write “Mrs. Sarah Johnson” by adding “rs. Sarah Johnson” after the printed M.

This tradition developed when formal correspondence followed stricter rules of etiquette and titles were routinely used when addressing guests. Instead of printing a separate space labeled “Name,” hosts could simply provide an “M” followed by a blank line, allowing guests to complete their appropriate title and name themselves.

Modern wedding invitations don’t always use this format. Many couples now replace the “M” with something clearer such as “Name(s)” or simply leave a blank line. Some invitations also provide more inclusive wording because not every guest uses a title beginning with M.

So there is nothing complicated hidden behind that mysterious letter. If an RSVP card has an “M_____” line, it traditionally means you should complete your title and write your name on the line. It’s simply an old piece of wedding etiquette that has survived into modern celebrations.