Variation is the norm in language. It is the universal trait that has never been embarrassed by counterexamples. As language is a joint product of human cognition and human society, the dimensions underlying language variation could potentially reveal the complexity of the human mind and defines us of what we are as cognitive and social beings, be it Austrians speaking German, or Nepalis speaking Dumi. This volume includes eight papers highlighting three dimensions underlying language variation. The linguistic dimension explores how language changes across the physical time span and...