A stoa (/ˈstoʊə/; plural, stoas, stoai, or stoae /ˈstoʊ.iː/), in ancient Greek architecture, is a covered walkway or portico, commonly for public use. Early stoas were open at the entrance with columns, usually of the Doric order, lining the side of a building; they created a safe, enveloping, protective atmosphere.
This, an "open-fronted shelter with a lean-to roof", is the meaning in modern usage, but in fact the ancient Greeks "made no clear distinction in their speech" between these and large enclosed rooms with similar functions.