本题考查词典的含义。alphabetical——字母顺序。

The dominant sense of the word dictionary for English-speaking people is a book which presents in alphabetical order the words of English, with information as to their spelling, pronunciation, meaning, usage, rules of grammar, and in some, their alphabetical.
对于说英语的人来说，词典的主要意义是一本按字母顺序列出英语单词的书，包括它们的拼写、发音、含义、用法、语法规则，在某些情况下，还有它们的字母顺序。

故答案为alphabetical。