It goes without saying that vocabulary plays a vital important role in our daily life, and plays more significant role in junior students’ learning process. Vocabulary is one of the three essential elements of language-pronunciation, vocabulary and grammar, and it is the fundamental element in the course of foreign language teaching. McCarthy even said that “No matter how well the student learns grammar, no matter how successfully he masters the sound of a language, without words to express a wide range of meanings, communication in that language cannot happen in any meaningful way.”(Zhang 2)
For a great number of students, vocabulary acts as a stumbling block on the road leading to their free use of English. Especially for junior high school students, the size of vocabulary boasts a prominent position in their English vocabulary learning. However, limited vocabulary often hinders some students’ learning motivations when they are reading or communicating with others in English. High volumes of words lays a solid foundation for their English study not just in junior school but in a life time.

II. Definition And Classification of Vocabulary

2.1 Word，Word Formation and Vocabulary  
According to Hu Zhuanglin, word formation concerns two ways at the level from morpheme to word, they are the inflectional way and the derivational way. Inflection indicates grammatical relations by adding inflectional affixes, such as person, case, number(61). For instance,
(a) Person: say/says; think/thinks
    (b) Case: Lily/Lily’s; school/school’s
    (c) Number: banana/bananas;
The derivation way involves the process of how words are formed. There are two sub-types: the derivational type or Derivation and the compositional type or Compound. Derivation represents the relationship between roots and affixes: 浅谈初中英语词汇教学技巧(2):http://www.751com.cn/yingyu/lunwen_35646.html