What is a small structure with a window that projects out from a sloping roof called?

A small structure with a window that projects out from a sloping roof is known as a dormer. Dormers are typically used to add natural light and usable space to the upper levels of a building, particularly in attic or loft areas.

They have a vertical window set in a structural element that extends out from the roof plane, providing light and headroom to spaces below. By incorporating a dormer, the overall aesthetic of the building can also be enhanced, contributing to its architectural style.

In contrast, a bay window generally projects outward but differs from a dormer in that it is usually part of the main wall structure instead of being set within the sloping roof. A skylight is a window installed in a roof or ceiling that allows light to enter from above but does not project outward. An awning, on the other hand, refers to a secondary covering attached to the exterior wall of a building that typically provides shelter from the elements; it is not a window structure.