This is a book about practical key competencies consisting of basic management knowledge, business skills and mindsets, assuming those who have just started working for companies, people who are thinking of starting up businesses and students interested in business as readers. These key competencies are a selection of 52 business keywords, beginning with the letters from A to Z. Although each is a basic content in doing business, all the keywords are considered important management knowledge, skills and mindsets. It is becoming more important to appropriately choose, integrate and demonstrate these key competencies in various business situations. Furthermore, I refer to theories and books that seem like classics, in modern fast-changing business environments. Picking the old brains is a shortcut to coming up with your answers. However, you should not simply take advantage of the wisdom as it is, but rather, modify it to suit your environments and use it in your own way. This book can hopefully provide some useful tips on how to succeed in business, how to deal with problems or challenges at work and how to lead a meaningful life through jobs.