Amphitheater
2 of the 7 encyclopedias on this shelf carry an entry for Amphitheater. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a double theater. The ancient theaters were nearly semicircular in shape; or, more accurately, an amphithey were half ovals, so that an theater, theoretically, consisting of two theaters, placed with their concavities meeting each other, was, loosely speaking, a nearly circular, or, more precisely, an oval building. Amphitheaters were first constructed of wood, but in the time of Augustus stone began to be employed. The place where the exhibitions took place was called the arena (Lat.=sand), because it was covered with sand or sawdust. The part next the arena was called podium, and was assigned to the emperor, the senators, and the ambassadors of foreign nations. Among the sights were combats of wild beasts and gladiator fights. The Romans built amphitheaters wherever they went. Remains of them are still to be found in various parts of Europe; but the most splendid ruins existing are those of the In recent years Coliseum at Rome. numerous elaborate amphitheaters have been built by some of the larger universities in the United States. These are used chiefly for athletic contests. Elaborate amphitheaters have also been erected as memorials, of which one of the finest examples is the amphitheater in the National Cemetery at Arlington.
Aiton's Encyclopedia (1910)
a spacious elliptical building used by the Romans for games and wild beast shows. The term is composed of amphi, meaning both, and theater. The seats of the Greek theaters occupied one side only of an ellipse, while the stage held the center. In the Roman amphitheater, both sides of the ellipse, that is to say, the entire border, were seated. See Colosseum; Thebes 2026 Editor's Note: The Roman amphitheater is the direct ancestor of every modern sports stadium — a bowl of tiered seats around an arena. Its greatest survivor, the Colosseum , is now one of the world's most-visited monuments, and Rome lights it up whenever a death sentence is commuted somewhere in the world. (Ed: BR 2026-07-18)