Recall that the notion of relations and functions, domain, co-domain and range have been introduced in Class XI along with different types of specific real valued functions and their graphs. The concept of the term ‘relation� in mathematics has been drawn from the meaning of relation in English language, according to which two objects or quantities are related if there is a recognisable connection or link between the two objects or quantities.
If you think you are learning any mathematics from this book, you are lying to yourself. This book prepares you to outsmart an 8-year-old, and be outsmarted by the watchman of Allen, FIITJEE