Invitation notation is a set of guidelines used to communicate the details of an event. The three most common terms used in invitation notation are 'CASUAL, ' 'BYOB, ' and 'RSVP.' 'CASUAL' is a six-letter word that indicates the dress code for the event, usually meaning that guests should dress in comfortable clothing. 'BYOB' is a four-letter acronym that stands for 'Bring Your Own Beverage, ' meaning that guests should bring their own drinks to the event. Finally, 'RSVP' is another four-letter acronym that stands for 'Repondez s'il vous plaît, ' which is French for 'Please Respond.' This term is used to remind guests to respond to the invitation so that the host knows how many people to expect.