The situation in which a phenomenon being observed for study is unwittingly influenced by the presence of the observer.

Learning that occurs as a function of observing, retaining and, in the case of imitation learning, replicating novel behavior executed by other people.

An area of a tall building, often open to the sky, from which the public may look at the surrounding panorama. / A building (such as a hide) from which people may observe wildlife.

(astronomy) The extent of a universe within the cosmological horizon of an observer.

a lookout or vantage point

Ferris wheel

plural of observation wheel

plural of observable universe

(rail transport) A railway passenger car made so as to facilitate seeing the scenery en route, sometimes with glass sides or with a kind of open balcony at the rear.

plural of observation car