Humour is a funny thing - everyone knows it but no-one knows what it is. This book addresses the question ‘What is humour?’ by first untangling the definitions of humour, amusement and funniness before then providing a new theory of humour which draws upon recent research in philosophy, psychology, linguistics and neuroscience. The theory is built up without assuming any prior knowledge and illustrated through humorous examples which are both entertaining and educational for anyone curious about what makes things funny. The book is then an accessible illumination of joking matters from dinner tables to online platforms to comedy clubs.