This book is a part of a series of 3 books written to provide complete coverage of the NCERT Science syllabus for classes 9 prescribed by the Central Board of Secondary Education (CBSE). The 3 books in this series are Science for Ninth Class (Part- L): Physics, Science for ninth Class Part-2): Chemistry Science for Ninth Class (Part-3): Biology. The most important feature of the revised editions of these books is that many solved and unsolved questions have been included to assess the students’ learning abilities. The main aim of bringing out this series is to make science more attractive, interesting, and understandable. The headings, subheadings, and definitions of each topic of this book have been given in different colors. This will help the students to locate the various topics easily and learn the definitions conveniently.