In the United States, "bathroom" commonly means "a room containing a toilet". In other countries this is usually called the "toilet" or alternatively "water closet" (WC), lavatory or "loo". The word "bathroom" is also used in the U.S. for a public toilet (the more formal U.S. term being "restroom").

In the United States, bathrooms are generally categorized as a "full bathroom" (or "full bath"), containing four plumbing fixtures: bathtub, shower, toilet, and sink; "half (1/2) bath" (or "powder room") containing just a toilet and sink; and "3/4 bath" containing toilet, sink, and shower, although the terms vary from market to market. In some U.S. markets, a toilet, sink, and shower are considered a "full bath". This lack of a single, universal definition commonly results in discrepancies between advertised and actual number of baths in real estate listings. An additional complication is that there are currently two ways of notating the number of bathrooms in a dwelling. One method is to count a half bathroom as ".5" and then add this to the number of full bathrooms (e.g., "2.5" baths would mean 2 full baths and 1 half bath). The other, newer method is to put the number of full bathrooms to the left side of the decimal point and to put the number of half bathrooms to the right of the decimal point (e.g., "2.1" would mean 2 full baths and 1 half bath; "3.2" would mean 3 full baths and 2 half baths).

Types of bathrooms

A bathroom directly connected to a bedroom is often called an en-suite bathroom. Its use is primarily intended for the occupants of that bedroom only. In French the term "en-suite" literally means "a following", in this case referring to the bathroom being part of the bedroom to which it is attached. A bathroom adjacent to or directly connected to a master bedroom in a private home is generally called a master bathroom, unless it is shared by other bedrooms or is the only bathroom in the home. An en-suite bathroom attached to two bedrooms is sometimes referred to as a "Jack and Jill bathroom". Travelers often get confused regarding different types of bathrooms when booking rooms in hotels and bed and breakfast accommodation. Some common questions relate to en-suite, "private" and "shared" bathrooms (sometimes called "facilities"). Both en-suite and private bathrooms are for the exclusive use of the occupants of a particular bedroom. An en-suite bathroom is accessed from within the bedroom, however, whereas a private bathroom is accessed from outside the bedroom but is normally adjacent or near to the bedroom. A shared bathroom is a bathroom outside of any bedroom that is shared between guests staying in two or more separate bedrooms. Although the word bathroom may be used, this can refer to a room with a shower rather than a bath. The bathroom would also normally include a toilet as well as washing facilities.