They are not, however, homogeneous, each having its own dialect divisions.
For the same reasons, dialect divisions that earlier would have widened into distinct languages are now unlikely to do so.
In fact, dialect divisions must have been a feature of linguistic communities as early as there is any knowledge of them.
The fragmentation of Northwest Germanic can be dated roughly to the period of the 3rd 6th centuries with the development of three major dialect divisions: in Scandinavia, North Germanic; in Jutland and the northwest of Germany, North Sea Germanic; and in central Germany, South Germanic.
Each division includes several dialects.
The division into Northern and Southern dialects must be very old.
The rise of France extinguished most of Germanic control west of the Rhine, a process facilitated by German divisions; German dialects remain in use in France only in Alsace and parts of Lorraine.
After this division the two groups developed distinct dialects differing chiefly in the pronunciation and written symbolization of vowels.
Boundaries between dialect areas are gradual, but in Norway the divisions are usually given as East (Lowland, Midland), Trönder (around Trondheim), North, and West.
This uniformity has led many linguists to deny the meaningfulness of such a notion altogether; very frequently, however, bundles of isoglosses or even a single isogloss of major importance permit the division of a territory into regional dialects.
