What is a shop at the front of a Roman house that has an opening onto the street called?

A shop at the front of a Roman house that has an opening onto the street is known as a taberna. This term specifically refers to various types of shops or workshops located in the urban environment of ancient Rome, often serving commercial purposes. A taberna could sell food, wine, or other goods, allowing householders to engage directly with the public and contribute to the bustling street life of a Roman town.

The other terms listed refer to different architectural elements or spaces in a Roman house. Fauces, for instance, is the term for the narrow corridor or entrance that leads into the house, typically from the street. Piscina refers to a fish pond or a pool, usually found in larger estates or close to baths, and it is not directly related to commercial activities. Hortus means garden, an area designated for plants and relaxation within a property, rather than a business space. Thus, the correct answer distinctly reflects the function and design of urban spaces in ancient Rome.