A coaxial field system is a group of fields (usually square or rectangular in plan) arranged on a single prevailing axis of orientation. Most of the field boundaries either follow this axis (axial boundaries) or run at right angles to it (transverse boundaries and terminal boundaries). The length of the axial boundaries in relation to the system as a whole can vary, and only in smaller systems do they run all the way from one end to the other. The degree of in-filling also varies between examples to the extent that coaxial field systems with many transverse boundaries have what amounts to a grid-like arrangement. However, the dominance of the main axis in the layout is always clear (Fleming 1987,188).
Coaxial field systems typically cover an area in excess of 100 ha. Where preserved, the ends of a system are usually marked by terminal boundaries. The axial, transverse and terminal boundaries of coaxial fieldsystems variously comprise stone walls, ditches, banks, lines of post- and stake-holes or lynchets.
Coaxial field systems can sometimes be confused with other classes of field systems, notably regular aggregate field systems. Coaxial field systems can be differentiated by the fact that all the fields within a single system are aligned in the same direction, and because they cover much larger areas - anything from 100ha up to 10,000ha. It should also be noted that although some of the so-called "Celtic fields" of southern England fall within the class of coaxial field system as defined here, many of them do not.