Regional dialects are studied by mapping the geographical distribution of linguistic variations, such as different pronunciations. Lines are drawn between areas where different variations are found, called isoglosses. The family tree model implies isoglosses should not intersect, but in reality they often do intersect. Dialectologists have concluded each linguistic variation has its own distribution, and there is no reason to expect all variations to have identical boundaries. Therefore, isoglosses do not necessarily delimit distinct dialects except in trivial cases of a dialect defined by just one feature.

1. Regional dialects and isoglosses
• How clear are the boundaries between
varieties?
• The hierarchical model of the family tree
implies that the boundaries between varieties
are clear at all levels of the tree.
• It is possible to continue such a tree
downwards, revealing smaller and smaller
varieties, until one comes to the level of the
individual speaker (the 'idiolect'). ???

2. • REGIONAL DIALECTS
• DIALECTOLOGY
• Dialectologists have been studying the
geographical distribution of linguistic items,
such as pairs of synonymous words (for
example, pail versus bucket), or different
pronunciations of the same word, such as
farm with or without the I r l.

3. • The results are plotted on a map, showing
which items were found in which villages.
• Why villages?
• Dialect geography tends to concentrate on
rural areas to avoid the complexities of towns.
• The dialect geographer may then draw a line
between the area where one item was found
and areas where others were found, showing
a boundary for each area called an ISOGLOSS
(from Greek iso- 'same' and gloss- 'tongue').

4. • The family tree model allows a very important
prediction to be made regarding isoglosses,
namely that they should not intersect.
• Distinctions can add further subdivisions
within a variety, but they cannot subdivide
two varieties at the same time for the simple
reason that a tree diagram can show
subclassification, but not cross-classification.
• However, cross-classification is the normal.

5. • Keeping in view the findings, many dialectologists
have drawn the conclusion that each item has its
own distribution through the population of
speakers, and that there is no reason to expect
different items to have identical distributions
(Bynon, 1977). This seems to be the only
reasonable conclusion to draw from the data.
• But this leads to the further conclusion that
isoglosses need not delimit varieties, except in
the trivial sense where varieties each consist of
just one item.

6. • Thanks