In Real Estate Rentals, to what does "Number of Units" refer?

[TurboTaxEsther]

For example, if you have a rooming house and rent to 4 people it would be 4 units.

If you have a duplex, it could be 2 units. 

Most of the time there is only one unit. IE a family of four renting a house would be one unit. The house is one unit. If the same house had a basement apartment that is rented to another person, the house would have 2 units. 

[rollydus]

So, in our principle residence, if we rent a room to a student, that is 2 units. And our rental property is 1 unit, regardless of how many renters live there. Is this correct?

[TurboTaxEsther]

Renting one room to a student is one unit. You don't count yourself.  And yes, the rental property is one unit regardless of how many people live there.

[TurboTaxEsther]

If you rented 2 rooms to 2 students, that would be 2 units.