This is a practical guide to common problems in English grammar and usage. It is written for foreign students who would like to know more about English, and who want to avoid mistakes. It is written Especially for intermediate students, but more advanced learners may also find it useful. The explanations are made as simple as possible. The book describes standard modern British English, and gives realistic examples of spoken and written language (both formal and informal). There are some information about American usage, but the book is not a systematic guide to American English. This is a dictionary of problems, not a grammar. Points are explainded in short separate entries, so that you can find just the information you need about a particular problem - no more and no less. Entries are arranged alphabetically and numbered. A complete index at the back of the book shows where each point can be found.