People speaking common language. Sharing common culture and living in certain specific geographical region for a long time to develop emotional bondage for one another.
When narrow mindness is created in them, it is called regionalism.
As language, religion, life style, traditions being similar, emotional bondage of people residing in same area becomes stronger.
The people who create and instigate regionalism are harmful elements for national unity and integrity.
The States Reorganisation Commission already implemented the recommendation of divisions as per the linguistic barriers. Language stimulates regionalism.