Several word lists have been developed to provide people with a limited vocabulary either for the purpose of rapid language proficiency or for effective communication. These include Basic English (850 words), Special English (1,500 words), General Service List (2,000 words), and Academic Word List . Some learner's dictionaries have developed defining vocabularies which contain only most common and basic words. As a result word definitions in such dictionaries can be understood even by learners with a limited vocabulary.    Some publishers produce dictionaries based on word frequency  or thematic groups.