The sulung was the basic unit of assessment for the public obligations in Kent, serving the same purpose as hides in the remaining counties of Wessex and western Merciaand of carucates in most of the Danelaw counties.
The sulung was divided into yokes. Like the corresponding units in other counties, sulung and yoke were derived from the vocabulary of ploughing, sulung from the Old English word (sulh) for a plough, yoke from a pair of yoked oxen, hence four yokes to the sulung. Although it appears to have contained twice the number of customary acres as the hide and carucate, the sulung was assessed for the public obligations at the same rate as these units.
For more detail, see J.H. Round, Feudal England (1895).