Monsieur and Sir

Monsieur noun - Used as a French courtesy title; equivalent to English `Mr'.

Sir and monsieur are semantically related in gentleman topic. In some cases you can use "Sir" instead a noun "Monsieur", when it comes to topics like lord.

Sir noun - Term of address for a man.

Monsieur and sir are semantically related in gentleman topic. You can use "Monsieur" instead a noun "Sir", if it concerns topics such as mister, lord.