The fifth edition has been revised and updated to give explanations of key terms and concepts that school and college students will encounter when working for GCSE, Standard Grade or other qualifications at this level. The extensive revision brings the book in line with recent changes in the National Curriculum and examination syllabuses and new initiatives in teaching. The entries have been revised, expanded and updated and the text redesigned in full colour. Alphabetical arrangements of entries encourage quick reference and a system of cross-references supports each entry so that it can be put in context.