There is a tendency to describe the stonework of a wall as either "random" or "coursed". However there are many tens of thousands of miles of wall in Britain and the large mileage of wall which would then fit into each of these categories means that there must be huge variations on a theme, especially in areas with complex geology such as North Wales and the Lake District. Whilst trying to categorise every subtle variation would be nigh on impossible, some generalisations can be made. In addition you also find some very distinct patterns, such as herringbone and polygonal, which whilst they might be coursed - as with herringbone, or random (as is the case with polygonal walls) are distinct enough to merit a mention in their own right.
There are no standard definitions for patterns of dry stone work, although there are British Standards for masonry (mortared) walls. Many masonry terms are used to describe dry stone work, although they do not always 100% and this can lead to some confusion where masonry terms are directly applied to dry stone walling, or used within the specifications for a dry stone wall. The most notable example of this is the masonry distinction between "ashlar" - that is square hewn stone, generally sawn sandstone, and all other stone which regardless of type or shape is described as rubble. This is hardly ideal when applied to dry stone walling, where stone is almost never as regularly shaped as ashlar and rubble is used either to describe very irregular (often smallish) stone, or a less formalised building pattern. This said we need to make some basic distinctions between the two main patterns - coursed and random: Coursed walls are those where the stones are set in layers of single stones of more or less the same height within any single layer. It is tempting to define a random wall as any pattern which is not coursed, and essentially this is the case, although something along the lines of walls where the height of adjacent stones in any one layer can vary considerably is a little more technical. *****SOME SORT OF DIAGS****