What classifies as a "unit" in NYC?

[Raymond Chan]

I've always been confused by the term "unit" in Real Estate. When people talk about 1,2,3... unit buildings, what exactly makes something a "unit."

My father said that every unit has a bathroom, but he isn't too sure. 

Any thoughts?

[Tom Chen]

From what I could gather...a rentable apartment.

So a unit could be 1, 2, or 3 bedrooms...

A 2 family house is 2 units.

A 3 family house is 3 units.

If you take a 1 family and legally separate t into a 2 family, that'll be 2 units.