classification

Dear members,

(1)  I am interesting in knowing *the* hypothesis that has been used to classify languages, for instance, PIE --> Latin --> French;  PIE --> Sanskrit --> Hindi.


(2) When a clear-cut distinction is not made (for example, it is not possible, using *this* hypothesis, to decide whether language X belongs to Latin-branch or Sanskrit brach), decisions are made using independent considerations or using hypotheses from different domains. If the latter is so, which other hypotheses have been used?

References, any websites that discuss the above, and your comments are welcome.

Best Regards,
Brice Gnahoui.