Studies of British field systems are at present in a somewhat paradoxical position, Above all the debate about the terminology of field systems has reached a critical phase. It seems that there exists a serious danger that British agrarian studies may once again flounder on the rocks of terminological ambiguity. This terminological controversy highlights two of the pitfalls facing all studies of agrarian history: first, the myopic nature of the search for mono-causal explanations; secondly, the fallacious nature of the assumption that from a similarity of function and even of genesis. It is in one sense annoying that, after H. L Gray's classic work was published, there is still no agreed terminology for studies of English field systems. In another sense it is inevitable, for numerous subsequent studies have demonstrated the diversity of British field systems, both in space and in time. Nevertheless we need to set a uniform terminology of field systems in order to escape from the paradoxical situation. If we are to attempt to arrive at any general conclusions, then we must construct an agrarian terminology, The definitions of agrarian terms could be formulated in terms of three sets of criteria : formal defInitions based on morphology, functional definitions based on organizational relationships and genetic definitions based on the origins of agrarian forms and structures, There are, however, some confusion in adoption of the definitions, For example, H. L. Gray's 'Midland open-field system' was a formal definition based on morphology, But In his definition, the form of fields has been confused with their functioning. A similarity of form cannot be taken as an indication of a similarity of function or of genesis, As same manner, R. A Butlin thought that the term 'common field' could serve as a standard term with relation to field system, in preference to the other term, 'open field', And he also thought that the term 'field system' should be replaced with the term 'common-field husbandry', But this suggestion would seem to be unacceptable, in that it implies that all field systems were variants of common-field husbandry. Before going further to deal with the specific terms 'open field' and 'common field' two general problems must be mentioned. First, there could be the spatial variations in agrarian terminology. Secondly, there are the temporal variations in agrarian terminology, the problem here being the changes in the meanings of terms through time. Indeed the agrarian terms may change its meaning both spatially and temporally, being used in historical records to refer to different types of agrarian structures at different places and at different historical periods. Finally, it is necessary to consider in more detail the terms 'open field' and 'common field'. A R. H, Baker suggested that even as a formal definition the tenn 'open field' is so confusing that a pattern of unenclosed strips and parcels within enclosed fields might better be termed 'subdivided fields' rather than 'open fields'. ]. Thirsk has also argued that fields comprised of unenclosed parcels not definitely known to have been cultivated or grazed in common are best described as 'open fields', the tenn 'common fields' being best reserved for fields over which common rules of cultivation and grazing are known to have operated, As j. Z. Titow persisted, however, the terms 'open field' and 'common field' are freely interchangeable, for there are no differences in form and meaning between them. A single explicit reference to a piece of land lying 'in the common field' or in communi campo is sufficient enough to indicate the presence of the open-field system, and it is apparent that the field system means common-field system The term 'common' referred in historical records in relation to open field means the function of common rights in land using under common-field system as well open-field system The two terms 'common-field system' and 'open-field system' is same thing, in that the two have same features of agriculture in essence but they are differentiated each other in non-essential aspect Therefore it is reasonable to adopt the tenn 'open-field system' as a standard about agrarian systems in medieval England To conclude, this attempt will set up a terminological framework and solve the terminological problems of British field systems.