Jugerum

Iugerum, jugerum, iugera or iugus (in Latin, the last form, as a neuter noun of the third declension, is very common in the oblique cases and in the plural) was a Roman unit of measurement of area, 240 pedes (Roman feet) or 71.0 m in length and 120 pedes or 35.5 m in breadth, containing therefore 28,800 pedes quadratum. That is 0.623 acre or 0.25 ha.

It was the double of the Actus Quadratus, and from this circumstance, according to some writers, it derived its name. It seems probable that, as the word was evidently originally the same as iugum, a yoke, and as actus, in its original use, meant a path wide enough to drive a single beast along, that iugerum originally meant a path wide enough for a yoke of oxen, namely, the double of the actus in width; and that when actus quadratus was used for a square measure of surface, the iugerum, by a natural analogy, became the double of the actus quadratus; and that this new meaning of it superseded its old use as the double of the single actus.