Psychological knowledge is often applied to the assessment and treatment of mental health problems, it is also directed towards understanding and solving problems in several spheres of human activity. By many accounts psychology ultimately aims to benefit society. The majority of psychologists are involved in some kind of therapeutic role, practicing in clinical, counseling, or school settings. Many do scientific research on a wide range of topics related to mental processes and behavior, and typically work in university psychology departments or teach in other academic settings. Some are employed in industrial and organizational settings, or in other areas such as human development and aging, sports, health, and the media, as well as in forensic investigation and other aspects of law. The book "Principles of Psychology" has been especially written according to the requirements of the syllabus. The text of this book has been written uniquely and comprehensively that has been discussed in such a simple way that the students will find no difficulty to understand and learnt about it. The author shall be thankful to the readers who point out errors and omissions which inspire of all care might have been there.