Private Apartment is a residential unit located in a building occupied by more than one residential unit, built by non-governmental entities. When people refer to Private Apartment, usually it means those with less communal facilities in the Singapore context. (see condominium)
The term "apartment" is favored in American influenced countries whereas the term "flat" is sometimes, but not exclusively used.

Some apartment-dwellers own their own apartments, either as co-ops, in which the residents own shares of a corporation that owns the building or development; or in condominiums, whose residents own their apartments and share ownership of the public spaces. Most apartments are in buildings designed for the purpose, but large older houses are sometimes divided into apartments. The word apartment connotes a residential unit or section in a building. In some locations, particularly the United States, the word denotes a rental unit owned by the building owner, and is not typically used for a condominium.

The types of units in private apartments and condominiums are
studio room units - A small apartment usually consisting of one main living space, a small kitchen, and a bathroom.
1 bedroom units
1+1 - 1 bedroom units with 1 maid / study room
2 bedroom units
2+ 1 - 2 bedroom units with 1 maid / study room (2+1)
3 bedroom units
3+ 1 - 3 bedroom units with 1 maid / study room (3+1)
4 bedroom units
4 + 1 - 4 bedroom units with 1 maid / study room (4+1)
Penthouses - A large residential unit located at the highest level of a building with a roof garden.
Maisonette - A 2-level residential unit in a building. The adjoining floors of the units are connected by an internal staircase in the house.

Master bedroom / master room - the principal bedroom, usually is the biggest room in the house and comes with attached bathroom

Utility room / maid room/ study room - smaller room in the house, usually not used if there are other available rooms

Common room - mid-sized bedroom, most commonly available type of room for rental