In some structures, one door leads into the main body of the building. In others, however, a separate entry space serves as a passage between the outer door and the interior of the building. This entry space can be referred to as either a foyer or a vestibule. A space like this adds a sense of formality to the structure. It can also serve as an energy saving measure, as the space between the main door and the interior door can help keep heated or cooled air inside the home as people enter and exit.
By definition, a foyer and a vestibule are the same. Both are defined as a space that separates the main building or home from the outside, commonly having a separate interior door. Because they are synonymous, the terms foyer and vestibule are commonly used interchangeably. There are some differences between these two terms, however.
Entrance Into Language
The term vestibule has been in the English language longer, entering in or around 1726, according to Merriam Webster. The term foyer wouldn't come in to use for another 100 years, entering the language in 1833, reports the same source.
The term vestibule comes from the Latin word vestibulum, which means "forecourt" or the courtyard before the entrance to a house. Foyer originally came from a Latin word meaning "hearth" but before entering English usage passed through French.
While the denotation, or dictionary meanings, of these words may be almost identical, the connotation, or implied meanings, differ slightly. Because the term vestibule is commonly used to describe grandiose structures with high ceilings and intricate designs, calling this space a vestibule adds a sense of formality to the space. A foyer, on the other hand, is commonly seen as a plainer space that is less formal and features less interesting architecture or design elements.