The bay window

A bay window (Erker) — the part of a façade that projects beyond the main plane. It can take various shapes (round, rectangular, polygonal) and span one or more floors. It's carried on cantilever beams; if the support continues down to the foundation, it's already a risalit.

The photo shows a home renovation in Canada. Architecture by Drew Mandel Architects.

One half of the façade keeps its traditional bay window untouched, while the other half merges the bay with a dormer to form a larger projecting volume with floor-to-ceiling windows. It's a great example of reinventing an existing façade with minimal intervention.