In the Roman Republic and the Roman Empire, the Latin word castrum (plural castra) referred to a building, or plot of land, used as a fortified military base. In English, the terms "Roman fort", "Roman camp" and "Roman fortress" are commonly used for castrum. However, scholastic convention tends toward the use of the words "fort", "camp", "marching camp" or "fortress" to translate castrum. For a list of known castra see List of castra.