What characteristic distinguishes a townhouse?

A townhouse is specifically characterized by its shared common vertical walls with one or more adjacent homes. This architectural style is designed for higher density living, where multiple residences can be built in a row or cluster, sharing walls for efficiency and cost-effectiveness. Each unit typically has its own entrance and is often privately owned, but the shared walls are a key feature that differentiates townhouses from other types of residential properties, such as single-family homes or detached homes, which do not have shared walls.

The other choices do not accurately define what distinguishes a townhouse. Properties that have no shared walls cannot be classified as townhouses as they lack the defining feature of being connected to other units. The presence of a yard may vary, with some townhouses including small yards or patios while others may not have significant outdoor space at all. Finally, townhouses can be multi-story homes rather than being limited to a single-story design. Thus, the correct identification of townhouses centers on their unique architectural elements, specifically the shared walls.