Concept: Many people have a monolithic concept of English and other languages
A person with very strong monolithic assumptions about language might believe some of the following:
Each language is a single object
Each language has clear boundaries
Each language has an unambiguous shape and form
Each language is uniform and stable
Few people, and almost certainly no language teachers, will believe all these statements without exception. But monolithic assumptions like these often underlie materials, tests, and our classroom practices, as well as the expectations and practices of our learners.