in terms of word frequency, different dictionaries use different methods to represent their word frequency. We can see from the headword below that Longman Dictionary of Contemporary English uses the symbols s2 and w1 to show the 3000 most important words to know. s2 means that the word is one of the 2000 most common words in spoken English. W1 means the word is one of the 1000 most common words in written English. However,Oxford Advanced Learner's Dictionary uses a "key" symbol to show that the word is a part of the Oxford 3000 list of important words.