A household includes all of the people who occupy a housing unit. (People not living in households are classified as living in group quarters.) A housing unit is a house, an apartment, a mobile home, a group of rooms, or a single room occupied (or if vacant, intended for occupancy) as separate living quarters. Separate living quarters are those in which the occupants live separately from any other people in the building and that have direct access from the outside of the building or through a common hall. The occupants may be a single family, one person living alone, two or more families living together, or any other group of related or unrelated people who share living quarters.

In 100-percent tabulations, the count of households or householders always equals the count of occupied housing units. In sample tabulations, the numbers may differ as a result of the weighting process.

A subfamily is a married couple with or without own children under 18 years old who are never-married, or a single parent with one or more own never-married children under 18 years old. A subfamily does not maintain their own household, but lives in a household where the householder or householders spouse is a relative. Subfamilies are defined during processing of sample data.

In some labor force tabulations, both one-parent families and one-parent subfamilies are included in the total number of children living with one parent, while both married-couple families and married-couple subfamilies are included in the total number of children living with two parents.