This book contains various useful definitions of the terms to which one often come across during his or her study of chemistry. It is always difficult to understand concepts without knowing the key terms. This book is a sincere effort from authors to help the students who are studying or planning to study chemistry in detail. The authors have tried to their best to cover most of the terms. This book will also serve the purpose of a quick revision guide for those who are appearing for any competitive exam or a job interview. Best wishes to the users.