A wordbook is a list of words and their meanings or a list of words with their matches in another tongue. In some tongues, words can have many sundry shapes, but only the main shape of a word, the 'headword', is listed.
For most tongues that are written with the Latin staffhoard, the words are listed staffwise from A to Z. Other tongues may list the words in another way. For show, Chinese lists words by how many strokes it takes to write the staff of that word.