comparative linguistics 
plural noun [treated as singular]
The study of similarities and differences between languages, in particular the comparison of related languages with a view to reconstructing forms in their lost parent languages.Such sound shifts in comparative linguistics parallel, almost uncannily, the slow march of genetic mutations as offspring populations gradually separate from a parent stock....
- These historical and philosophical puzzles cannot be solved by turning to current scholarship in comparative linguistics or cognitive science, because those literatures are also in some disarray.
- Is this not another example of the pitfalls of comparative linguistics?