•Stop translating - The most important reason to start using a dictionary that only has English in it is the same reason teachers insist you use only English in the classroom. If you can switch off the L1 part of your brain in class it will eventually become possible to think in English and so speed up your comprehension and production of the language. Using a monolingual dictionary not only means you are reading in English and avoiding your own language, but that you can also copy the definition down into your notebook and so increase your use of English outside class as well.
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