Final answer:
A French-speaking man is formally addressed as 'Monsieur', which is similar to 'Mr.' in English.
Step-by-step explanation:
The form of address used for or to a French-speaking man is Monsieur. This is the equivalent of 'Mr.' in English and is used regardless of marital status. When addressing a person, it is customary to use their title followed by their last name. In the context of letters or formal greetings, you might begin with 'Dear Monsieur [Last Name]'. It is also considered polite and respectful to use the highest-ranking title the person possesses if they have multiple titles, e.g., 'Dear Professor [Last Name]' or 'Dear Dr. [Last Name]'. On the other hand, addresses like 'Mme' (Madame) are for married women and 'Mademoiselle' for unmarried women, although the latter is being used less frequently in contemporary French due to its association with marital status.