I got a wedding invitation this morning and thought filling out the RSVP card would take about ten seconds. There were the usual choices for accepting or declining, but then I noticed something I had never paid attention to before: a large “M” followed by a blank line. I stared at it wondering whether it meant “meal,” “married,” or something else entirely.

After asking a few people, I was even more confused because nobody seemed certain. Some thought I was supposed to write the number of guests attending, while another person suggested it might be asking for my middle initial. As it turns out, the explanation is much simpler—and it comes from traditional wedding etiquette.

The “M” is the beginning of the courtesy title that goes before your name: Mr., Mrs., Ms., or Miss. The guest completes the appropriate title and then writes their name on the remaining line. For example, someone named John Smith could complete it so the line reads “Mr. John Smith.”

The tradition comes from an era when formal titles were routinely used on wedding correspondence. Rather than printing several possible titles on the response card, stationers could simply provide the shared first letter “M.” Modern invitations sometimes replace the entire convention with a straightforward “Name(s)” line because it is easier to understand and accommodates guests who use other titles.

So there was no secret wedding code hiding on my invitation after all. The “M” simply prompts you to write your title and name, while the separate yes-or-no section tells the couple whether you will attend. Once you know what that tiny letter means, the strangely confusing RSVP card suddenly makes perfect sense.