In architecture, pavilion has several meanings;

• It may be a subsidiary building that is either positioned separately or as an attachment to a main building. Often it is associated with pleasure. In palaces and traditional mansions of Asia, there may be pavilions that are either freestanding or connected by covered walkways, as in the Forbidden City (Chinese pavilions), Topkapi Palace in Istanbul, and in Mughal buildings like the Red Fort.
• As part of a large palace, pavilions may be symmetrically placed building blocks that flank (appear to join) a main building block or the outer ends of wings extending from both sides of a central building block, the corps de logis. Such configurations provide an emphatic visual termination to the composition of a large building, akin to bookends.

The word is from French pavillon (Old French paveillon) and it meant a small palace, from Latin papilionem (accusative of papilio). In Late Latin and Old French, it meant both ‘butterfly’ and ‘tent’, because the canvas of a tent resembled a butterfly's spread wings.

The word is from the early 13c., paviloun, "large, stately tent raised on posts and used as a movable habitation," from Old French paveillon "large tent; butterfly" (12c.), from Latin papilionem (nominative papilio) "butterfly, moth," in Medieval Latin "tent" (see papillon); the type of tent was so called on its resemblance to wings. Meaning "open building in a park, etc., used for shelter or entertainment" is attested from 1680s. Sense of "small or moderate-sized building, isolated from but dependent on a larger or principal building" (as in a hospital) is by 1858.