The Latin word castra, with its singular castrum, was used by the ancient Romans to mean buildings or plots of land reserved to or constructed for use as a military defensive position. The word appears in both Oscan and Umbrian (dialects of Italic) as well as in Latin. It may have descended from Indo-European to Italic. In classical Latin the word castra always means "great legionary encampment", both "marching", "temporary" ones and the "fortified permanent" ones, while the diminutive form castellum was used for the smaller forts, which were usually, but not always, occupied by the auxiliary units and used as logistic bases for the legions, as explained by Vegetius. A generic term is praesidium ("guard post or garrison"). The terms stratopedon ("army camp") and phrourion ("fort") were used by Greek language authors, in order to designate the Roman castra and the Roman castellum respectively. In English, the terms "Roman fortress", "Roman fort" and "Roman camp" are commonly used for the castra. However the scholars' convention always requires the use of the word "camp", "marching camp" and "fortress" as a translation of castra and the use of the word "fort" as a translation of castellum and this type of convention is usually followed and found in all the scholarly works.