I believe the answer is: bond with different countries
When we bond with different countries, a cultural assimilation would happen among the countries that involved. When this happen, people from each countries will start to adopt each other's language and create a major change to both existing language.
The five major ways language can change are adaptation, synthesis, standardization, genesis and design. In adaptation, words that are commonly used are being shortened. Words that are borrowed from other language is an example of synthesis while a word becomes regular as time passes in standardization process. New words are made to express new ideas in genesis and design are more on language using technical terms.
