When the book tells you that the word is in the top 50 most common words in spoken English but much lower in written English, that isn't a guess. It's data.
: The text includes over 3,000 authentic examples of language in use rather than invented sentences. longman student grammar of spoken and written english pdf vk
However, it is essential to note that downloading copyrighted materials without permission may be illegal in some countries. Moreover, the quality and accuracy of the PDF version may vary depending on the source and the scanning or conversion process used. When the book tells you that the word