In most American homes, the bathtubs/showers are combined with the toilet and sink because the average small house “bathroom” is usually no larger than 5 feet by 7 feet = roughly 1–2/3 meters by 2–1/3 meters. This puts the 5 foot bathtub width-wise at the end, with the toilet beside it on one length-wise wall, and the sink beside that. The door, then, is usually lined up with the open floor space, leaving just enough depth for the counter/cabinet surrounding the sink (where most of the storage is found) and the depth of the toilet. This is the standard size for a house of less than 2,000 square feet (approx. 667 meters), which is the standard size for the average middle- to low-income home.
Most Americans refer to the “lavatory” in a house as a bathroom, even if it has a shower instead of, or none. Bathrooms that contain only a sink and toilet, no bathtub and no shower, are described as half-baths. Most public lavatories are referred to as restrooms, or comfort stations or men’s rooms or ladies’ rooms. Lavatories on ships are generally referred to as the head. Euphemisms include “going down the hall,” “visiting the litter box,” and “had a nature call.”