Forms are not a catalogue of the techniques (vocabulary) of the system. It also contains a set of principles (grammar) of the system (such as to use a kick to set up a punch). When you learn "This is a book", you should be able to construct sentences such as: - This is a pen. - This is not a book. - That is a book. - ... The ability to remember "this is a book" may not be as important as the ability to "create" your own sentences by using the same grammar - subject, verb, article, object.