According to Veg. Mil. 3,8 (Nam a castris diminutivo vocabulo sunt nuncupata castella) the castella are relatively small camps that are probably distinguishable from the permanent auxiliary camps and tended to be established in a rather ad hoc manner to secure supplies or as part of a larger fortification (Veg. Mil. ibid.). Castella are probably comparable in size and number of garrisons with the ‘small citadels’ of the limes or the burgi (Veg. Mil. 4,10: castellum parvulum, quem burgum vocant).
Herz, Peter (Regensburg),
Huß, Werner (Bamberg) and
Pingel, Volker (Bochum),
Brill’s New Pauly, Antiquity volumes edited by: Hubert Cancik and , Helmuth Schneider, English Edition by: Christine F. Salazar, Classical Tradition volumes edited by: Manfred Landfester, English Edition by: Francis G. Gentry.
Consulted online on 22 October 2020 <http://dx.doi.org/10.1163/1574-9347_bnp_e228620>