Frommon(“my”) +sieur, from the oblique case ofOld Frenchsire (cf. alsoseignor), ultimately fromLatinsenior. The first syllable has been reduced through frequent use. Loss of word-final/r/ was common in Early Modern French, but failed to establish itself except in (most) words in-er.Monsieur andgars are two relics of this pronunciation habit.
A custom held that it was impolite to useMonsieur with a family name (e.g.Monsieur Dupont) in direct address from a hierarchical inferior to a superior, unless it was needed to disambiguate. Instead, one should simply address the person asMonsieur. This custom may now be obsolete.
Unlike in English,Monsieur is frequently used without a name or article as a polite reference to a man in the third person, notably in official registers:
Monsieur s’est présenté à l’urgence à 18 h 12.
The/This gentleman/The patient/Mr. [name] attended the emergency room at 6:12 p.m.
Additionally,Monsieur (andMadame) are sometimes used in conjunction with titles/roles in formal registers.
Monsieur le Directeur fera une annoncement à 13h30.
The director will be making a presentation at 3:30pm.
Madame le Président a prononcé un discours en lequel elle a dit que la guerre n’est pas juste.
The president has made a speech in which she said that the war is unjust.
Althoughun/le monsieur is used as a common noun to mean "a/the gentleman", using the wordune/lamadame to mean "a/the lady" is considered childish language. Instead,une/ladame is used.
