Formal:
* Господин (Gospodin): This is the most formal and common way to address a man, similar to "Mr." in English.
* Уважаемый (Uvajaemy): This means "respected" and is used in formal situations, often in written correspondence or when addressing someone in a position of authority. It is followed by the person's name or title.
Informal:
* Товарищ (Tovarishch): This is a less formal term that was popular during the Soviet era, roughly translating to "comrade." It's still used sometimes, but it's not as common as it used to be.
* Друг (Drug): This means "friend" and is a very informal way to address someone, typically used only with close acquaintances.
Other options:
* Господин Иванов (Gospodin Ivanov): You can also use "Gospodin" followed by the man's last name, similar to "Mr. Ivanov" in English.
* Иван Иванович (Ivan Ivanovich): If you know the man's patronymic (middle name), you can use the full name, which is the most formal way of address.
The best choice will depend on the situation and your relationship with the person you are addressing.