Mr. is the abbreviated form of the title Mister when used with a name. The plural is Messrs. (For comment on Mrs. and Ms., See madam.) Examples: "Mr. Seth Mieley and Mrs. Alix Greenway won the dance contest." "Mmes. (or Mesdames) Fogarty and Sloan and Messrs. Nieley and White attended the play." "Since I don't know and don't care whether Barbara is married or single, call her Ms. Barbara Kenneally."
Dictionary of problem words and expressions. Harry Shaw. 1975.