Soffit describes the underside of any construction element. Examples of soffits include:

• the underside of an arch (whether supported by piers or columns),
• the underside of a flight of stairs,
• the underside of a projecting cornace, or
• the underside of a ceiling to fill the space above the kitchen cabinets, at the corner of the ceiling and wall,
• the exposed undersurface of any exterior overhanging section of a roof eave.

In popular use, soffit most often refers to the material forming a ceiling from the top of an exterior house wall to the outer edge of the roof, i.e., bridging the gap between a home's siding and the roofline, otherwise known as the eaves.

Soffit exposure profile (from wall to fascia) on a buildings' exterior can vary from a few centemeters (2-3 inches) to well beyond a meter (3 feet) depending on construction. It can be non-ventilated or ventilated for cooling non livable attic space.