R.S.V.P. four little letters that you often see on invitations, program announcements and meeting notices. But do you know what they mean? I've had youth and adults both ask me "What does R.S.V.P. mean?"

R.S.V.P. stands for the French phrase, "repondez, si'l vous plait," which means "respond, if you please." In modern language, the request is to "please reply." In this short abbreviation, the person sending the invitation is asking that you tell him whether you accept or decline the invitation. In other words, will you be coming to the event, or not?

According to etiquette experts, every social invitation that you receive requires a response. The exception to the rule is the invitation that asks you to pay money to attend, such as a benefit, a fundraiser or an auction. Every other invitation should receive a response from you within a week. For those who are planning an event, this is important from a practical point of view because they need to know how many people to count on and how many supplies to purchase.

More important, though, is the simple courtesy of responding to someone who was nice enough to invite you, even if it is to say that you will not be able to attend. Your response also will put the hostess' mind at ease, knowing that you received the invitation and are aware of the event. Here's a personal example: My family celebrated a graduation and a wedding in 2008, and I was surprised at the number of invited guests to both events who did not respond in any way at all. It left me wondering if they had even received the invitation or if it had gotten lost in the mail.

Many formal invitations, including most wedding invitations, now include a printed reply card for your response. Send it back promptly, again within a week's time. (An etiquette side note it wasn't that long ago that enclosing a reply card was considered in poor taste. However, nowadays, most people are so remiss in their manners that it has become necessary and quite acceptable to include this built-in reminder to respond.)

If no reply card is enclosed, a formal invitation will include response instructions in the lower-left corner. If there is a phone number, you may call to accept or decline the invitation. If only an address is given, you must write your response. Passing the host on the street or in the office hallway and saying, "I can't be there" doesn't count. You should still respond according to the instructions on the invitation.

R.S.V.P. why French? You might wonder why we use the initials of a French phrase in an invitation written in English. You could say that the French "invented" etiquette, with many of our modern practices originating in the French court of King Louis XIV in the late 17th and early 18th centuries.

Judith Martin, author of etiquette books and a syndicated newspaper columnist known as "Miss Manners," thinks that R.S.V.P came about as a polite way of reminding people of something that they should already know if you receive an invitation, you need to reply.

More information is available in my Living Well blog at http://SWKTalk.com/livingwell.